Verse 13. You are the salt of the earth.
There are two properties in salt : to give savour, and to preserve from corruption. What is termed savour in food (sapor) is wisdom in man, and expressed by the word salt. What is called in other things conservation (conservatio) is in men confirmation in good lives, and is termed in the inspired writings edification. The Apostles are called the salt of the earth, therefore, because they are men, and ought to teach by their wisdom, and edify by their lives. S. Augustin (i., De Serm. Dom.) shows why Christ spoke the above words. He had urged the Apostles before to the highest perfection of life: “Blessed are the poor in spirit;” and He desired to show that they ought to aim at being such, because they were the salt of the earth. By the earth here, S. Augustin says, men are to be understood. This is also certain from the custom of Scripture.
This is more necessary of observation because, as S. Chrysostom and Theophylact have said, the Apostles were called the salt of the earth, as about to be the masters, not of one man, or of a few men, but of the whole world (Matt 14:15).
St. Mark (9:50) and St. Luke (14:34) relate that on another occasion Christ used the same comparison. But it is an easy and probable conclusion that He did this, not once only, but frequently as the case required, as we often do in our teaching.
But if the salt have lost its savor. μωρανθη—Infatuatum fuerit: that is, loses its savour and sharpness. Doctors of the Church do this when they either teach wrongly or build up badly.
Wherewith shall it be salted? That is, the salt itself (St. Matt 9:50); for there is no salting of salt. If the teacher teach amiss, by whom shall he be taught? If he live badly, by whom shall he be corrected? for there is no doctor doctorum. Not that the teacher cannot be corrected, but it is not usual nor easy.
But to be cast out. To be trodden under foot by the passers-by, as things thrown out into the streets. The meaning is that other things, even if they have lost their natural virtue, are still useful for other purpo.ses. Gold money is broken up—it is no longer money, but it is still gold; it will not serve for commerce, but it is useful to the goldsmith. Food is tainted—it is not set before men, but it may be given to the dogs. A garment is worn out, it is thrown on to the dunghill—it will no longer warm men, but it will enrich the ground. But salt, if it has lost its savour, is useless for the dunghill, and will not manure the ground—nay, it makes it sterile (Ps 107:34; and St. Luke 14:35). That which is of the most use, when decayed, becomes the most useless. The branch is most necessary for the production of fruit, but if it wither nothing is more valueless (Ezek 15:2, 3, 4).
Verse 14. You are the light of the world. You who ought to enlighten the world by your doctrine and example; the world has no teachers of goodness but you. Christ probably meant by the three words—salt, light, and the city—to signify one and the same thing. This, as we learn from S. Jerome, was the custom of the Syriac, which was the language He used (Note: Aramaic = Syriac). Not only here, but in many other passages, we see Christ using many similes, one upon another, to express the same thing. Of this S. Matthew (chapter 13) gives many examples. One thing must be observed, that Christ was the one only true Light “which enlighteneth every man that cometh into the world ” (St. John 1:9; 3:19; 8:12; 9:5; 12:35, 36).
Christ is called the true Light because He is the supreme Light in Himself, with whom, if not the Apostles alone and other holy men and Doctors, yet St. John the Baptist, than whom there was none greater among those born of women, may compare. But the other John said truly, he was not that light; yet of him the Evangelist writes: “He was a burning and a shining light” (John 5:35). As in this passage of S. Matthew the Apostles are called the light, all Christians are called the same (Philippians 2:15; Ephes 5:8; 1Thess 5:5). Christ is the Light by His own nature: others by His grace and gift, because they are enlightened
by Him : Christ, because He lightens every man that cometh into the world, not only extrinsically by His example and doctrine, but also by His intrinsic grace: the Apostles, as lighting others, not only by their example, but also by their doctrine ; Christians by their example.
A city cannot be hid. The first part of the comparison is wanting. You are a city, or like a city, placed on a hill. St. Jerome shows that the Apostles and Prophets are the mountains, because, being on high places in the Church, they are seen by all. The Author also observes that they are described as towers (Ps 122:7), although the meaning here is a mystical one, the literal being different. In the same sense they are here compared to a state (civitati), or rather to a city (urbi).
“Cannot.”—That cannot, you ought not to, be hidden. Christ does not admonish them to live uprightly lest they give offence, because their example, like a city on a hill, cannot be hid; but He warns them not to conceal themselves.
Verse 15. Neither do men light a candle. The meaning of these words is clear. Their object is not—so S. Jerome thinks—that Christ uttered them to give the Apostles courage and confidence to preach the Gospel freely; as if one should exhort a champion to fight strenuously and with courage, because the eyes of all were upon him. Others think that He intended to warn them to live circumspectly, lest they should give offence—for a city set on a hill cannot possibly be hid.
Nor were they to resemble a candle put under a bushel, but one placed in a candlestick, which cannot but be seen by all (St. Paul to the Philippians 2:15, and 1 Peter 3:16). S. Chrysostom and Theophylact explain it thus: Christ’s meaning seems to be, to exhort the Apostles to shine brightly both by word and example, and not to spare their labour. Besides, He had kindled them as lights; that is. He had made them Apo.stles, and had therefore placed them above others, as a city on a hill, that they might be conspicuous, and shine, and teach, and not be hid. For a city is not built upon a mountain that it may not be seen, nor is a candle lighted that it may be hid under a bushel, but that it may be placed in a candlestick, and light all, and be seen by all. Christ says this in other words (St. Luke 2:49), and S. Paul exhorts S. Timothy “to preach the Word ” (2 Tim 4:2). The words that follow—”So let your light shine—confirm this opinion. The words “under a bushel” are put, probably, because a bushel was very fit for concealing the light. So Luke 8:16.
Verse 16. So let your light shine. Christ elsewhere seems to teach the contrary (Matt 6:1, 2, 5), and many things in that place to the same purport. The answer is easy. The word ” that ” in this instance does not show the cause, but the result, as in John 9:39 and 1Cor 11:19. St. Chrysostom (Hom. 10. on Romans; Hom. 27 on 1Cor., and on S. Paul’s words, “There must be heresies”), John Damascene, with other authorities of the Greek Church, say that the word is not causative, but illative. For Christ did not command the Apostles to act rightly that they might be seen by men, which chapter 6 forbids; but so to live that every one who saw their actions might glorify, not them, but their Father who is in heaven, and of whose grace it was that they did them. This is not forbidden in that 6th chapter of St. Luke.
Is it not lawful, then, ever to do good that we may be seen by men, when we should not otherwise do it? It is lawful if only we do it not for our own sakes, but for the sake of God. It is lawful with that object, but not as the final object to do good. It is lawful to come thither, but not to remain there; our minds must lead on to the glory of God. Before they came to God they stood still; nay, they fell. He who wishes to be seen by men when well-doing, wishes it not that he himself, but that his Father in heaven may be glorified—he wishes, not himself, but God to be seen. For no one wishes to be seen by men that he may merely be seen, but that he may be given some glory by being seen. If he seek not glory, or if he seek it not for himself, but for God, even if he desire to be seen, he does not appear to desire it. In this sense St. Peter wishes Christians who live righteously to desire to be seen by the Gentiles (1 Pet 2:12). In this sense Christ seems to have said: “Let your light so shine”. In this passage the word “that” signifies, not only the event and consequence, but the end and cause. He compared the Apostles to a candle; but the candle is lighted that it may be seen, and, as we have said, Christ does not there proceed as by leaps, but gradually: “Glorify your Father who is in heaven”.