The following is excerpted from Father Anthony John Maas’ (1859-1927) Commentary on the Gospel According to Matthew. He authored numerous articles in the Catholic Encyclopedia. His wide knowledge of scripture commentators from the early church to his own day will be readily apparent to anyone who reads this post. Father Maas usually abbreviated the names of author he was citing or critiquing, so I tried to give their full last names in this post but found it quite time consuming and stopped.
Summary of Matthew 5:1-16~This section refers to the citizens of the Messianic kingdom, but for convenience’ sake it may be subdivided into the following parts: 1. Introduction [Matt 5:1-2]; 2. character of the citizens both in themselves [Matt 5:3–6] and in reference to others [Matt 5:7–12]; 3. influence of the citizens both to preserve [Matt 5:13] and to guide [Matt 5:14–16] others.
Mat 5:1 And seeing the multitudes, he went up into a mountain, and when he was set down, his disciples came unto him.
Introduction. Here we become acquainted with the time, the place, the occasion, the nature, and the hearers of the following discourse. a. The time is implied in the clause “and seeing the multitudes.” For these must be those mentioned in the preceding chapter as coming from Galilee, Decapolis, Jerusalem, Judea, and from beyond the Jordan. It is extremely probable that they are identical with the multitudes mentioned in the third gospel [Lk. 6:17].
Reasons: [a] They come from nearly the same place; [b] many commentators maintain their identity: Bede, Thomas Aquinas, Salmeron, Tostatus, Maldonado, Jansenius, Lapide, Grimm, Schanz, Fillion, Keil, Mansel, etc.; [c] the discourse of our Lord pronounced on the occasion has the same beginning and end, and treats of the same subject in both the first and third gospel; [d] it is true that some commentators leave this question of identity to the judgment of their readers [e.g. Cornely], that others regard the identity as doubtful [Augustine, Rabanus], and that others again clearly deny the identity of the two discourses [Anselm of Laon, Albert, Toletanus, Barradus Sylveira, Arnoldi]; but their arguments are not Strong enough to convince us:  The omission of the legal discussions in the third gospel is in keeping with the class of readers for whom it was written, since Gentiles would not have been able to understand the bearing of these points; hence St. Luke has only 30 verses, while St. Matthew has 107.  If according to the first gospel Jesus ascends a mountain, while according to the third he descends before addressing the multitudes, we remember that he had prayed the whole night at the very top of the mountain where he chose the twelve apostles in the morning. From here he descended to a level place on the mountain where he met the multitudes, so that the report of both the first and the third gospel is correct.  It is not true that our Lord held the discourse before the election of the twelve according to the first gospel, and after the election according to the third: the first gospel does not mention the election of the twelve, but only enumerates them Mt. 10:2, so that there can be no contradiction between Matthew and Luke on this point.
The identity between the discourse of our Lord as contained in Mt. 5–7 and Lk. 6:27–49 once established, we may determine the time of the discourse from the third gospel. After settling in Capharnaum in the beginning of the second year of his public life, Jesus caused the miraculous draught of fishes, and called the four disciples [Lk. 5:1–10]. Then follows the healing of the demoniac, of Simon’s wife’s mother, of other sick people, the first missionary journey through the cities of Galilee, the cleansing of the leper, the return to Capharnaum, the healing of the paralytic, the call of Levi, and the feast in his house [cf. Mk. 1:21–2:22]. After this comes the Pasch with its details as described in Jn. 5:1–47. After Easter, Jesus passes with his disciples through the cornfields, has an encounter with the Pharisees, heals the withered hand in the synagogue whereupon the Pharisees conspire against him, works the miracles by the seaside, and is followed by the multitudes; finally he ascends a mountain, spends the night in prayer, chooses the twelve, and on descending meets the multitudes on the mountain-level where he delivers the discourse now under discussion [Mk. 2:23–3:19].
He went up into a mountain. b. The place of the discourse. Jer. has nothing certain about the mountain, but believes that it is either Thabor or any other prominent mountain in Galilee; he excludes, however, the opinion of certain “simple brethren” who identify the mountain with Mount Olivet. Euthymius concludes from the Greek article that the mountain must have been well known to the readers of the evangelist, and is inclined to infer from this that it was somewhere near the city of our Lord. Others see in the expression an opposition to Mt. 4:13, where our Lord is represented as acting on the seashore; but there is too great an interval between 4:13 and 5:1. An old tradition which seems to have come down from Brocardus  identifies the mountain with the Kurun Hattin, or the Horns of Hattin. This mountain lies about midway between Thabor and Capharnaum, almost facing Tiberias, and a journey of about three hours from the Sea of Galilee. We may be allowed to take the following description of its site from Stanley’s Sinai and Palestine [p. 436]: “Skirting the hills of Galilee, on the east, is an undulating tableland, which is broken by a long, low ridge, rising at its northern extremity into a square-shaped hill with two tops, which give it the modern name of the ‘Horns of Hattin,’ Hattin being the village on the ridge at its base. This mountain or hill—for it rises only sixty feet above the plain—is that known to pilgrims as the Mount of the Beatitudes, the supposed scene of the sermon on the mount.… That situation so strikingly coincides with the intimations of the gospel narrative that, in this instance, the eye of those who selected the spot was for once rightly guided.” Though on the west side the height of the hill does not exceed forty feet, it rises on the northeast about four hundred feet above the surrounding plain. Besides, each of its horns tapers to a height of about thirty additional feet; between the two horns is a saddle-like plain, 400 paces long, capable of containing a considerable audience, and furnishing a charming view over the surrounding country. Among the mountains west of the Sea of Galilee, Kurun Hattin is the most considerable, and deserves more than any other the Greek title “the mountain.” Jesus ascended this mountain not to escape the multitudes [Cajetan, Maldonado], but to gain a suitable position for teaching them [Albert, Thomas Aquinas; cf. Mt. 7:28; Lk. 6:19]. The sermon on the mount may therefore, even as to the locality of its delivery, be compared with the law of Sinai: both were given on a mountain; the one by the ministry of angels, the other by our Lord himself [cf. Heb. 2:2; Gal. 3:19]; the one was written on stone tables, the other on the heart of men [cf. 31:33]; the one addresses slaves, the other sons; the one begins with terror, the other with blessings; the one threatens punishment, the other proposes rewards [Pasch.]; the one is accompanied by thunder and lightning, and no one is allowed to touch the mountain; the other is given with the greatest peace and serenity to people pressing around the Word incarnate [Jansenius Syleira].
And when he was set down. c. Occasion and audience of the discourse. Jesus has chosen the twelve from among the large number of disciples who had followed him, and, descending from the top of one of the horns, meets the multitude in the saddle-like plain. He sits down, after the manner of the Jewish teachers, in a spot that commands the whole plateau; his twelve surround him immediately; then come the disciples, and around them the vast multitude forms an enclosing circle. It is therefore not necessary to distinguish between a discourse delivered on the mountain to the disciples [Mt.] and another delivered on the plain to the multitudes [Lk. cf. Augustine]; much less need we assume a protracted stay of Jesus on the mountain near Capharnaum [cf. Lk. 24:49; Acts 18:11], during which he gave the lessons of the sermon on the mount gradually [Lutteroth]. That the discourse as related by the first evangelist was not addressed to the disciples alone is evident from Matt 7:28; and similarly, the discourse contained in the third gospel [Lk. 6:20 ff.] was not addressed to the multitudes alone, because our Lord began to speak, “lifting up his eyes on his disciples.”
Mat 5:2 And opening his mouth he taught them, saying:
And opening his mouth. d. Character of the discourse. The solemn scriptural form “opening his mouth” calls attention to the importance of the subject [cf. Job 3:1; 33:2; Dan. 10:16; Acts. 8:35; Acts 10:34; Acts 18:14], and suggests that he who had hitherto opened the months of the prophets, now opened his own month to instruct his followers [Suarez, de legib. IX. ii. 6; cf. Heb 1:2; Augustine Rabanus], and that the following sublime doctrine on Christian perfection had never before been proposed [Maldonado]. But then the question arises, whether our Lord really delivered the whole discourse contained in the first gospel, cc. 5–7, on any single occasion. The reasons for answering in the affirmative are the following:—
 There is a perfect logical and oratorical order in the discourse: it describes first the citizens of the kingdom as to their character [5:3–12] and their influence [13–16]; secondly, it compares the new kingdom with the old, in general [17–20] and in special commandments [21–48]; thirdly, it describes the proper means to be employed in the new law, whether they be acts of devotion [6:1–18], or acts of will and intention [19–34], or again, modes of conduct [7:1–12]; finally, a warning against danger [7:13–23] and a contrast with the old law conclude the discourse [24–27]. We grant that the evangelist might have given this form to the instructions and precepts of our Lord delivered on divers occasions; but the following considerations appear to exclude this supposition.  It has been pointed out that this discourse is identical with that in Lk. 6:20 ff.; now, the whole of this latter was delivered on one occasion. This argument holds, even if the reader does not admit the identity of the discourse in the first with that in the third gospel; for the third gospel shows that our Lord held, at times, more lengthy discourses, so that we have no reason for presupposing a medley in Mt. 5–7 unless proofs be advanced for such a supposition.  The contents of the discourse render it very probable that it was delivered by our Lord as the first gospel relates it. For it was of the highest importance that the Jewish adherents of Jesus should know accurately in what relation the Christian dispensation was to stand with regard to the Synagogue; now, the explanation of this point forms the burden of the sermon on the mount as contained in the first gospel. Besides, the words of Mt. 7:28 imply that the discourse had been a continuous instruction.  Hence among the recent commentators Arnoldi, Schegg, Bisping, Schanz, Fillion, Keil, Knabenbauer, defend, at least as probable, the opinion that our Lord delivered the sermon on the mount on one occasion.  The circumstance that the first evangelist follows elsewhere a topological arrangement [cf. 8–10, 13] does not prove that he does so in cc. 5–7; if several portions of the discourse are in other passages of the gospels connected with different contexts [e.g. Mt. 5:13 in Mk. 9:49 and Lk. 14:34; Mt. 5:15 in Mk. 4:21 and Lk. 8:16; Mt. 5:18 in Lk. 16:17; Mt. 5:25 in Lk. 12:58; Mt. 5:29 in Mt. 18:9 and Mk. 9:46; Mt. 5:32 in Mt. 19:9 and Lk. 16:18; Mt. 6:9 ff. in Lk. 11:2 f.; Mt. 6:14 in Mt. 18:35 and Mk. 11:25; Mt. 6:20, 21 in Lk. 12:33, 34; Mt. 6:22 in Lk. 11:34; Mt. 6:24 in Lk. 16:13; Mt. 6:25 in Lk. 12:22; Mt. 7:2 in Mk. 4:24; Mt. 7:7 in Mt. 21:22, Mk. 11:24, Lk. 11:9 f. and Jn. 14:13; Mt. 7:13 in Lk. 13:24, 27], it must be remembered that our Lord repeated certain parts of his doctrine more than once. This is clear from the following passages that have evidently been repeated: cf. Lk. 8:16 and 11:33; Mt. 9:32 and 12:22; 12:38 and 16:4. Such repetitions are most natural, since Jesus taught in different localities and before different audiences. In the sermon on the mount we are prepared to admit a number of doctrinal and moral principles that occur elsewhere also, because this sermon is a kind of a summary of our Lord’s position with regard to the law. The length and the copiousness of matter contained in the sermon on the mount are no valid argument against its being delivered on a single occasion; coming, as it did, after the second Pasch of the public life of Jesus, his followers were prepared for it, and on account of their manner of learning, their memory was sufficiently cultivated to retain its doctrine.
Mat 5:3 Blessed are the poor in spirit: for theirs is the kingdom of heaven.
Blessed are the poor in spirit. 2 Character of the citizens. a. In themselves. The evangelist describes the citizens of the Messianic kingdom negatively and positively: negatively, they are not attached to the riches, to the honors, to the pleasures of this world; positively, they earnestly desire after the goods of the next world. Each of these points is further developed in the gospel.
A. Detachment from riches. This virtue is inculcated by the evangelist in the first beatitude.
[a] Our Lord begins with the promise of blessedness or happiness, after which all men are so earnestly striving, and by which all are so effectively attracted. The nature of this blessedness is more fully described in the immediate context: “for theirs is the kingdom of heaven.” We have already seen that the first evangelist designates by “kingdom of heaven” the Messianic kingdom promised in the Old Testament.
[b] The condition of the subjects to whom Jesus promises the possession of this kingdom corrects the corrupt Messianic idea of the Jews. For the citizens of the kingdom are not the rich and honored of this earth, but the poor in spirit. That the Greek word employed by the evangelist means “poor” is evident from Mt. 19:21; 26:9, 11; Mk. 10:21; 12:42; 14:5; Lk. 14:13; 16:20; etc. This meaning of the word is confirmed by the Old Testament passages Is. 61:1; 66:2; Ps. 4:2, 3; 72:4; etc.; cf. also 2 Cor. 8:2, 9; Apoc. 3:17. If further proof of our statement were needed we might point to Lk. 6:20, 24, where poor is used in opposition to rich. The classical meaning of πτωχός does not differ from its signification in Sacred Scripture: “poor, strictly, one who crouches or cringes … a beggar” is the interpretation of the word given by Liddell and Scott [s. v.]. Hilgenfeld and Köstlin are so thoroughly convinced of this signification of πτωχός that they reject τῷ πνεύματι as a later addition, appealing to Clementine Homilies, 15:10; Polycarp ad Phil. 2.
[c] The additional clause τῷ πνεύματι has been understood in various ways:  The word “spirit” applies to our intellect, so that the poor in spirit are the ignorant and the stupid [Julian, cf. Or. De princ. iv. 22; Luther. Fritzsche, Grimm Lex.]. St. Paul [1 Cor. 1:16, 17] and Barnabas 19 do not favor this interpretation, since they do not depreciate wisdom and knowledge on account of themselves, but on account of the accompanying pride and want of simplicity. Besides, the word “spirit” hardly signifies either intellectual endowments or acquirements.  Keil believes “poor in spirit” applies to those that are destitute of the Holy Spirit; need we say that those “in their knowledge destitute of truth, in their will destitute of holiness, in their feeling destitute of happiness” are supremely wretched rather than attractively blessed [Tholuck]?  Jerome, Rabanus Salmeron, understand by “poor in spirit” those that are poor by the grace of the Holy Ghost. Though this opinion is right as far as it goes—for πνεῦμα signifies in the New Testament either the Holy Ghost or the human soul imbued with the grace of the Holy Ghost [cf. Mt. 4:1; 12:31; 22:43; 26:41; Mk. 1:10, 12; 8:12; 14:38; Lk. 1:17, 80; 2:27; etc.]—yet it does not go far enough; for the Holy Ghost may inspire man in various ways as to earthly possessions.  What has been said excludes the opinion that the “poor in spirit” are those that are poor by their own choice, not by necessity [Chrysostom Anselm of Laon Cajetan, Jansenius, Maldonado, Sylveira Barradus, Calmet, Suarez de grat. lib. II. xxii. 5]. These are, at best, only a part of the poor in spirit.  The “poor in spirit” are all those whose mind and heart are wholly detached from the riches of this earth, whether they be really poor or use the goods of the world as if they used them not. This interpretation of the clause is confirmed by the following considerations: such a state of detachment cannot be reached by the unassisted human will; it is implied by the opposition to the rich, described in Lk. 6:24 as having their consolation in their riches, so that they are rich by reason of their attachment to their wealth; it is also implied by the repeated invitations of our Lord himself [Mt. 13:22; 19:21], which warn us against anxiety about the things of this world, and advise us to abandon our earthly goods in order to attain the true poverty of spirit. Again, this view is supported by overwhelming extrinsic evidence: Chromatius, Gregory of Nyssa, Basil, Paschasius, Anselm of Laon, Bruno, Arnoldi, Albert, Thomas Aquinas, Salmeron, Cajetan Jansenius, Maldonado, Lapide Barradus, Sylveira, Calmet, Fillion, Knabenbauer.  Since poverty of spirit as described is followed by humility, and since both together produce an intimate sense of our own spiritual destitution, the interpretation of Hilary, Chrysostom, Euthymius, Theophylact, Gregory Zachar. chrysop. Augustine, who identify the poor in spirit with the penitent and humble, and that of Ambrose [in Lc. lib. v. n. 53, 54], Leo [serm. 95], Jer. Bed. Rab. gl. ord. Pasch. Dion. Mar. who understand by poor in spirit both the actually poor and the humble, and finally that of Fab. Arn. Schegg, Reischl, Grimm, Schanz, Keil, op. imp. Alb. who understand by poor in spirit those that feel and bemoan their own spiritual helplessness, the obscurity of their understanding, and the weakness of their will: these interpretations may be regarded as giving the consequent meaning of the clause, though they miss the genuine sense.
Mat 5:4 Blessed are the meek: for they shall possess the land.
Blessed are the meed. β. Detachment from honors. The blessedness promised in the second beatitude consists in possessing the land. Since the possession of Palestine had been promised to the Israelites, both the national and the individual happiness of the Jews was connected with the fulfilment of this promise. It was on this account that the promises of the prophets Is. 60, 62, 65, 66, 30, 31, Zach. 14:7 ff., Ps. 37:11 etc. were of such vital importance to the Jewish community. Our Lord repeats in his second beatitude the promise of Ps. 36:11, in order to show that through him the national promises of Israel must be fulfilled.
[a] What land are the meek to inherit?  The land implies temporal prosperity [Chrys. Theoph. Euth.], so that it includes all earthly goods.  The promise refers only to the possession of heavenly happiness of which Palestine was a figure [Jer. Aug. Nyss. op. imp. Rab. gl. ord. Fab. Jans. Bar. Lap. Calm. Arn. cf. Rom. 8:21; 2 Pet. 3:12; Apoc. 21:2–5].  Palestine represented rather the Messianic kingdom than the future life in heaven; if then “the land” must be taken according to its typical meaning, our Lord promises entrance into the kingdom of heaven, or the kingdom of God, to the meek. And since the Messianic reign extends over both this and the next life, the promise of our Lord is not confined to either this or the next life, but repeats under a different form the blessing of the first beatitude.  We need not mention the opinions of those according to whom our Lord promises to the meek the perfect command over their own hearts, or the future glorification of their bodies, or the winning over of other men to their friendship, etc. [cf. Salm. t. 5, p. 66; Bar.].
[b] Who are the “meek” mentioned in the second beatitude? The meek [πραεῖς, עֲכָוִים] are repeatedly mentioned in the Old Testament, where they are assured of God’s special direction [Ps. 24:9], or salvation [Pss. 75:10; 146:6; 149:4], or of a share in the Messianic promises [Is. 11:4; 29:19; Ps. 21:28]. But it is especially in Ps. 36 [Heb. 37] that the expression finds a clear explanation; in fact, the second beatitude agrees with part of v. 11. In v. 9 the possession of the land is promised to those “that wait upon the Lord” [as opposed to “evil doers”); in v. 11 the same promise is made to the meek [as opposed to the “wicked” in 10]; in v. 22 the land is promised to “such as bless” the Lord [as opposed to such as curse him]; in v. 29 “the just shall inherit the land” in opposition to the unjust and the seed of the wicked in v. 28, and in parallelism to the Saints in the same verse; finally, in v. 34 those that “expect the Lord and keep his way” will inherit the land [in opposition to the sinners who shall perish forever]. It is therefore not without reason that we assign to πραεῖς [עֲכָוים] the meaning of meek; for meekness is primarily the virtue that regulates the passion of anger, not allowing it to exceed the boundaries of reason. The virtue of meekness falls, therefore, under the general head of temperance, just as detachment from earthly goods falls under the cardinal virtue of justice. In the first beatitude, therefore, those are called blessed that subdue their desire after earthly goods; in the second, those that bear patiently all earthly loss. And since contempt is practically the greatest earthly evil, the meek may be identified with those detached from the love of earthly honors.
Mat 5:5 Blessed are they that mourn: for they shall be comforted.
Blessed are they that mourn. γ. Detachment from pleasure. [a] The blessedness consists here in the promised consolation.  This consolation refers not merely to our eternal beatitude [Hil. Nyss. Arn. Alb. Caj.], but to this life also.  That the consolation refers to this life, also, is defended by Chrys. Aug. Jans. Lap. Knab. etc., and is based on the promises of both the Old and the New Testament. For though Apoc. 7:17; 21:4; Is. 66:6–14 may refer to the next life only, the promised consolation was so intimately identified with the Messias that even in the Rabbinic language the Messias is called the “consoler,” and the time of his appearance bears the name “consolation” [cf. Lightfoot, Hor. heb. ad Joann. xiv. 16]; even according to Lk. 2:25 the Messias is “the consolation of Israel.” This general hope was based on the promises contained in Is. 40:1, 11; 49:14 f.; 51:3 f.; 52:1 f.; 54:1 f.; 60:4f.; 61:1–3; 62:3; 65:18; etc. Our Lord therefore promises here again the entrance into the Messianic kingdom, but under a form corresponding to the moral condition of those to whom he makes the promise.
[b] The receivers of the third promise are those that mourn; mourning properly implies the presence of evil, since it is the effect of the will caused by the recognized presence of evil. That the sorrow implied in the passage of the gospel has a sacred character follows from Is. 61:3; Soph. 3:18 [heb.]; Ezech. 9:4. This evil is identified with our sins, by Hil. Chrom.; with our sins and those of our neighbor, by Chrys. Theoph. Jer. Leo, Bed. Br. Rab. Pasch.; with the evils of this life generally, by Nyss. Alb. Dion. Jans. Caj. Calm. Fil.; with the presence of the earthly evils and the absence of the heavenly goods, by Nyss. Bed. Ans. laud. Alb. Dion. Jans. Sylv.; in general, with the tears caused by the fear and the love of God, by Calm. [cf. Suar. de leg. IX. ii. 10]. As the first beatitude refers to a detachment from earthly goods that prescinds from their presence or absence, and as the second implies patient bearing of evil that is hard to remove, so the third refers to the pain of the will at the presence of any evil whatever, or to a perfect detachment from the feeling of pleasure.
Mat 5:6 Blessed are they that hunger and thirst after justice: for they shall have their fill.
Blessed are they that hunger and thirst. δ. Positive characteristic of the citizens. [a] The subjects of this beatitude have been identified in various ways:  Since Lk. 6:21 reads “Blessed are ye that hunger now, for ye shall be filled,” the words “hunger” and “thirst” have been applied to the feeling of bodily wants; the clause “after justice” is then explained as signifying “for justice’ sake.” Hence result the meanings: blessed are those that suffer hunger and thirst, because justice is denied them [cf. Mald.]; or because they fast voluntarily in order to acquire justice; or because they have to bear privations in order to comply with the demands of justice [cf. Lap. Jans. Calm.]. But the text of the gospel hardly permits this interpretation, since it represents justice as the object of hunger and thirst, not as the motive for bearing them patiently.
 Hunger and thirst must be taken metaphorically, so that they refer to spiritual, not to bodily wants. Am. 8:11 shows that such a metaphorical meaning of hunger and thirst is not unknown to the inspired writers; cf. Is. 55:1; Ps. 41:3; 62:2; Prov. 9:5; etc. As hunger and thirst surpass the other appetites of the animal life, so shall the desire after justice prevail over all the other longings of the citizens of the Messianic kingdom. Justice means here not only the special virtue which gives to every one his due, but implies the general virtue inclining our will to conform itself with the will of God. It may therefore be identified with holiness or perfection in general, comprising the observance of both God’s precepts and counsels.
[b] The blessedness promised in the fourth beatitude consists in the divine favor which God shows to all those that observe his holy will perfectly. This state of happiness had been predicted by the prophets as accompanying the Messianic kingdom: cf. Is. 4:3; 11:4; 42:3; 53:11; 23:5; 30:9; 31:33; 33:15; Ezech. 11:19; 36:26; Dan. 9:24; Os. 2:19; 3:5; Mich. 4:2; 7:18; Ps. 44:5; 71:4; etc. The promise, therefore, coincides again practically with the promise of entering the Messianic kingdom. Allusions to the manner in which this hunger and thirst will be filled we find repeatedly in the New Testament: cf. Jn. 4:13, 14; 6:35; 7:37; Rom. 7:24; 8:2, 4; etc. Hence the longing of those ardent souls shall be partially satisfied in this life, and perfectly in the next [op. imp.].
Mat 5:7 Blessed are the merciful: for they shall obtain mercy.
Blessed are the merciful. b. The citizens of the kingdom in their relation to others. The relation of the citizens may be considered under ordinary circumstances, or under external difficulties. a. Under ordinary circumstances the Christian life may be active, contemplative, or a combination of the active and contemplative. Each of these three cases is considered in the following three beatitudes: [α] The active life. [a] For the active Christian life our Lord recommends mercy, consisting not merely in forgiving the injuries done us by others, or in sympathizing with them in their trials and sufferings; but also in practically relieving them in their bodily and spiritual necessities [cf. Aug. Pasch. Br. Nyss. Jans. Sylv. Theoph. Caj. Jer. Chrom. op. imp. Fab. Dion. Bar. Suar. l. c. 14]. [b] Though the promise seems at first to give only a reward equal to the work [Chrys.], in reality it does not differ from the promises of the other beatitudes. For it must be remembered, in the first place, that the Messias is described by the prophets of the Old Testament as preëminently merciful [Ps. 71:12–14; Is. 11:4; 42:3; 50:4; 53:5; 61:1; Ezech. 34:16]. In the second place, the Messianic salvation was announced in the Old Testament as the principal work of God’s mercy: cf. Is. 48:11; 43:22–25; Ezech. 16:61–63; 36:32; Os. 2:19; Mich. 7:18–20; Soph. 3:19; Zach. 12:7, 10. The mercy therefore promised to the merciful is again a share in the Messianic salvation. [c] It must also be noted that Jesus opposes the current Pharisaic opinion concerning the Messianic kingdom in two ways. First, at the time of Christ, all earthly misfortune was regarded as the effect of personal sin [cf. Jn. 9:2], so that the foundation of all mercy was removed. Hence sprang the Jewish self-righteousness, and their proud disdain of all in misery [cf. Jn. 9:34]. Secondly, the Messianic kingdom is not only not due to the legal justice of the Jews, but is a work of pure mercy on the part of God, that will be given to those who do not despise the misery of their unhappy brethren. We need not point out the effect that these words of our Lord have produced in the Christian community in the form of innumerable institutions of charity and mercy [cf. Coleridge, The Public Life, ii. p. 240].
Mat 5:8 Blessed are the clean of heart: they shall see God.
Blessed are the clean of heart. [β] The sixth beatitude seems to be intended for the contemplative Christian life. This follows both from the subjects of the beatitude, and from the promise connected with it. [a] The description of the subjects opposes them to those only legally clean [cf. Mk. 7:3 f.; Mt. 23:25 f.], so that the hypocritical Pharisees are not included. But the clean of heart are not only the chaste [Theoph. Arn. Schegg], or the simple and upright of heart [Aug. Bed. Rab. Zach. chrys. Men. Lam. Schanz], or the chaste and simple [Mald.]; for had Jesus wished to designate these classes, he would no doubt have expressed them by their proper name, just as he names the merciful and the peacemakers [Bar.]. The phrase “clean of heart” signifies those that are not defiled by any stain of sin [Bas. reg. brev. 280; Nyss. Chrom. Hil. Jer. Leo, Pasch. Br. Arn. op. imp. Ans. laud. Alb. Fab. Tost. Dion. Caj. Salm. Jans. Lap. Suar. Bar. Sa, Sylv. Men. Gord. Coleridge, l. c. p. 271; Fil. Meschler, i. 294; Knab. etc.]. It may prove useful to refer to those Old and New Testament passages that are commonly connected with the subject of this beatitude: Ps. 33:4; 72:1; 50:12; Prov. 20:9; 24:7; Ezech. 11:19; 36:26; 1 Tim. 1:5; 3:9; 2 Tim. 2:22; 1:3; 1 Pet. 1:22.
[b] The promise made to the clean of heart corresponds with their spiritual condition. The expression is taken from the Oriental custom according to which kings were rarely seen in public, so that only their immediate surrounding and their familiar friends enjoyed the privilege of seeing their face continually. Moreover, the passage alludes to the Old Testament passages in which the prophets promise the Israelites the vision of a great light, of the glory of the Lord, of the salvation of God, of the beauty of God, of the king in his beauty [Is. 9:2; 33:17; 35:2; 40:5; 52:10; 60:2; 66:14; 66:18]. Impurity of heart is therefore to our power of seeing God what scales are to the eyes. The full vision of God is, of course, identical with the beatific vision, and reserved for the life to come; but even in the present life the pure of heart see the beauty of God, not merely in his revealed truth, but also in the objects of nature and in their own interior acts of mind and will. The happiness implied in the vision may be inferred from the observation of St. Augustin that “if the damned spirits could see for an instant the face of God, the pains of hell would come to an end.” We need not point out that contemplative souls especially enjoy the vision of God, even in this life, as far as this privilege is possible.
Mat 5:9 Blessed are the peacemakers: for they shall be called the children of God.
Blessed are the peacemakers. [γ] This beatitude regards especially the apostolic or the mixed life. For peacemakers are those that cause peace, and are, therefore, themselves at peace with God and men. [a] The word is understood in a general sense by Nyss. Chrom. Ambr. Jer. Br. Bed. Arn. Fab. Dion. Salm. Mald. Suar. Sylv. Lam. Calm. But the higher idea of causing men to make peace with God is added by Bas. Chrom. Theoph. Euth. Br. Dion. Salm. Jans. Reischl, Coleridge, Meschler, etc. This meaning of the word is in accord with Is. 53:7, where the excellency of the preachers of peace is described. Besides, the prophecies of the Old Testament announced the Messias as the great peacemaker [Ps. 71:3, 7; Is. 9:6, 7; 26:3, 12; 32:17; 52:7; 54:10, 13; 40:17; 66:12; 33:6, 9; Ezech. 34:25; 37:26; Mich. 4:3; 5:5; Agg. 2:10; Zach. 6:13; 9:10], so that in the language of Sacred Scripture peace must refer especially to the peace between God and man. Finally, the apostles are represented as the messengers of peace [Eph. 2:14; Col. 1:20; Eph. 6:15; Rom. 14:17–19; 2 Cor. 13:11; 2 Tim. 2:22; 1 Pet. 3:11–17].
[b] The promise made to the peacemakers consists in the sonship of God; for they would not be “called” children of God if they were not so in reality. The reasons for this reward of the peacemakers may be reduced to the following: peace is preëminently a characteristic of God [2 Cor. 13:11], so that the peacemakers resemble God in a special manner, and are therefore his sons or images [Nyss. Zach. Chrys. Alb. Mald. Dion. Calm. Fil.]. Again, the peacemakers do the work proper to Jesus Christ the Son of God, so that they may be said to share his sonship as they share his labor [Chrys. Theoph. Euth. Chrom. Br. Arn.]. The excellency and dignity of the sonship of God are well developed by Nyss. [De beatitud. or. 7].
Mat 5:10 Blessed are they that suffer persecution for justice’ sake: for theirs is the kingdom of heaven.
Mat 5:11 Blessed are ye when they shall revile you, and persecute you, and speak all that is evil against you, untruly, for my sake:
Mat 5:12 Be glad and rejoice for your reward is very great in heaven. For so they persecuted the prophets that were before you.
Blessed are they that suffer persecution. b. The citizens in time of trial. Jesus announces first the general principle that guides the Christian in his difficulties, and then applies this in a special manner to his apostles. a. The general principle [a] The experience of the just men of the Old Testament [Ps. 36:1; 38:2; 72:3; Job 9:22; 12:6], the history of the persecutions of the prophets [cf. Mt. 23:37; Acts 7:52], and the very words of the Messianic predictions [Ps. 44:4–8; Zach. 13:7; Joel 3:9 f.] rendered it more than probable that the citizens of the Messianic kingdom would have to undergo their special trials. The doctrine of our Lord on this point could, therefore, not scandalize his Jewish hearers, while it has been the comfort of the numberless Christian sufferers since the foundation of the Church.
[b] But mere suffering is not sufficient to render one the subject of this beatitude: “for what glory is it, if committing sin, and being buffeted for it, you endure?” says St. Peter to the early Christians [1 Pet. 2:20]. “But if doing well,” the apostle continues, “you suffer patiently, this is thank-worthy before God.” Aug. [Enarr. in Ps. 34:23] fully agrees with this: “it is not the suffering,” he says, “but the cause of the suffering, that maketh martyrs.” Similar observations are found in Aug. c. Gaudent. i. 20; op. imp. etc. The gospel expresses this cause in the words “for justice’ sake,” where justice signifies the whole complex of Christian virtues, both theological and moral [cf. 1 Pet. 4:15].
[c] The reward promised in this beatitude is really and formally the same as that promised in the first beatitude; but still the reason of the promise differs from that in v. 3: there the kingdom is promised to the poor on account of its riches, here the kingdom is promised to the persecuted on account of its honors and power [cf. Nyss. Arn. Schegg, Rom. 8:18; 2 Cor. 4:17]. Besides, the promise of the kingdom gives the form of a circle to the eight beatitudes, since they begin and end with the same promise [Coleridge, p. 348; Chrom.].
[d] That there are eight beatitudes is the common opinion of commentators, though Tost. Köstlin, Ewald, Hilgenfeld admit only seven, Jans, enumerates nine, and Delitzsch as many as ten. The numbers nine and ten can be obtained only by adding vv. 11, 12 to the beatitudes. The difference between these verses and the preceding has been pointed out by Aug. Ans. laud. Thom. Tost. etc. The beatitudes enounce general principles, the following verses are directed to the apostles [cf. infra] to whom they apply the last beatitude in a special way. Nor can we reduce the number of beatitudes to seven; though the promise of the eighth agrees with that of the first [cf. Tost.], the condition of the promise is entirely different in the two beatitudes. That seven is a sacred number in Scripture does not favor the opinion, because four and eight, too, are often used in a mystic meaning.
[e] Admitting, then, eight beatitudes, they have been variously classified by theologians and commentators.  Knab. is of opinion that they oppose the various Jewish prejudices concerning the nature of the Messianic kingdom. In point of fact, there can be no doubt that all the promises present either the whole Messianic kingdom, or some special part of it; the conditions, too, found in the single beatitudes are wholly opposed to the conditions which, according to Jewish ideas, were requisite for sharing the blessings of the Messias. But though this be granted, we cannot infer that our Lord followed a merely negative train of thought.  Aug. [De serm. in mont. i. 4, 11, 12], Rab. Zach. chrys. compare the beatitudes with the seven gifts of the Holy Ghost; this arrangement combines poverty with the fear of God; meekness with piety; mourning with knowledge; hunger and thirst for justice with fortitude; mercy with counsel; cleanness of heart with understanding; peacemaking with wisdom; the last beatitude returns to the beginning, and declares that man is perfect.  St. Thomas [la 2ae, qu. 69, a. 3] thinks the foregoing arrangement of the beatitudes follows the different motives of the virtues. He then proposes an order according to the matter of the beatitudes: knowledge and counsel direct the first five beatitudes; piety embraces mercy and hunger and thirst after justice; fortitude embraces meekness; fear contains poverty and mourning, by which man withdraws from the concupiscence and pleasure of the world.  In other passages St. Thomas proposes three more divisions of the beatitudes: the first rests on the various opinions of men concerning their happiness, which is placed by some in merely external goods, by others in the satisfaction of their desires [cf anger, of love of pleasure, and of ambition], by others again in the virtues of the active life, and finally, by a fourth class in the contemplative life. These four false views concerning happiness are contradicted in the eight beatitudes.  The second division rests on the effects of different virtues on our inner life: some remove our inordinate affections [avarice, anger, and pleasure]; others effect the doing of good works [justice and mercy]; others again dispose us for the most excellent spiritual gifts [purity of heart, peace, and suffering for justice’ sake].  The third division of the beatitudes views them according to their progress from external to internal goods: freedom from earthly possessions and from inborn passions is followed by external good works, by sentiments of compassion, by spiritual insight and order, and finally by patient suffering for justice’ sake [cf. St. Thom. Exposit. Mt.; in 3 sent. dist. 34, qu. 1, a. 4; Summ. 1a 2ae, qu. 69, a. 3].
β. Application of the last beatitude.  In v. 11 our Lord proposes three conditions of the special blessedness of the apostles. [a] They must bear insults, persecutions, and detractions; [b] these must be unjust in themselves; [c] they must be inflicted for our Lord’s sake [cf. Thom. Jans. Chrys. Euth. Knab. Schanz].  In v. 12 the special blessedness of the apostles is further developed: [a] they are to be glad and rejoice, even under their sufferings; [b] but the motive of this joy is their reward in heaven; [c] the promise of this reward is confirmed by the example of the persecuted prophets, concerning whose heavenly blessedness there could be no doubt. The joy of the apostles in their sufferings may be illustrated by Acts 5:41; James 1:2. Supposing the Catholic doctrine that a supernatural work is always performed with the aid of supernatural grace, we may conclude from this special promise that the apostles were by their suffering to merit, in the strict sense of the word, their heavenly glory. If the heavenly glory promised here to the apostles were a mere grace, and not a reward, Jesus would have used his words in a false meaning [cf. Jans. Schanz, Lap. Sylv. Caj. Br. Fil. Knab.]