Father Cornelius a Lapide (1567-1637) was a renowned exegete who wrote commentaries on all the books in the Catholic canon of Scripture, save Job and Psalms.
Note: Text in red, if any, represent my additions.
Mat 13:31 Another parable he proposed unto them, saying: The kingdom of heaven is like to a grain of mustard seed, which a man took and sowed in his field.
Mat 13:32 Which is the least indeed of all seeds; but when it is grown up, it is greater than all herbs, and becometh a tree, so that the birds of the air come, and dwell in the branches thereof.
The kingdom of Heaven is like to a grain of mustard seed, &c. Instead of the birds of the heaven lodge in the branches of it the Arabic has they are overshadowed by its branches. This is Christ’s third parable, the occasion and cause of which S. Chrysostom gives as follows: “Because the Lord had said that of the seed three parts perish, and one is preserved, and again of that which is preserved, there is great loss on account of the tares which are sown above it, lest people should say, who then and how many will believe? he removes this fear by the parable of the grain of mustard seed, and therefore it is said, Another parable put He proposed unto them, the kingdom of Heaven is like unto a grain of mustard seed, &c.”
You will enquire in the first place, what it is which is here compared to the kingdom of Heaven, and likened to a grain of mustard seed? 1. S. Hilary understands it of Christ Himself. He says, “The Lord compares Himself to a grain of mustard seed, which is very sharp and the least of all seeds, and whose virtue and power are increased by bruising and pressure. After this grain had been sown in the field, when it was taken by the people and delivered to death, as though in a field by a sort of sowing, there was the burial of its body, it grew above the measure of all herbs, and exceeded the glory of all the prophets. For like a herb the preaching of the prophets was given to Israel as being sick: but now in the branches of the tree, raised from the ground on high, the birds of the air dwell: by these we understand the Apostles, lifted up by the power of Christ, and they overshadow the world with their branches. To them the Gentiles flew for the hope of life; and when they are vexed with whirlwinds, that is by the blasts of the devil, they rest as in the branches of a tree.” In like manner S. Gregory (lib. 19 Moral. c. 11.) expounds this whole parable, “Christ Himself is the grain of mustard seed, who was planted in the sepulchre of the garden, and rose again a mighty tree. He was but a grain when He died; a tree when He rose again. A grain through lowliness of the flesh; a tree by the power of His majesty. A grain, because we saw Him, and there was no comeliness; but a tree because He was fairer than the children of men. The branches of this tree are sacred preachers. And let us see how widely they are spread. For what is spoken concerning them? Their sound is gone out into all the earth, and their words unto the end of the world. The birds rest in their branches, because holy souls who lift up themselves from earthly thoughts by the wings, as it were, of virtues are refreshed after the fatigue of this life by their words and their consolations.” You will say, how can Christ be called the kingdom of Heaven, when He is not the kingdom, but its King? It is replied: as a king is as it were the head in a kingdom, so a kingdom is as the body of a king. Wherefore a king represents the whole state or kingdom. Hence according to the rule of Ticonius, often in Scripture what belongs to the Church, which is the kingdom of Christ, is attributed to Christ, and vice versa.
2. More plainly and aptly, the kingdom of Heaven and the grain of mustard seed are the Church, especially the Primitive Church.
It’s important to keep in mind that although the Church and the Kingdom are closely associated they are not identical. The Church is the Kingdom present in mystery. The parable is applicable to the Church in this sense. The growth and fruition of the Kingdom is working itself out in and through the Church.
You will enquire: Why the Gospel is compared to a grain of mustard seed, and what are the resemblances between the two things? I answer, the first is that Christ by this parable intends to signify the immense power and fruitfulness of Evangelical preaching, insomuch that what had a very small beginning with Christ, and by a few Apostles, diffused itself over the whole world. For a grain of mustard seed is less than all seeds, i.e., the least of all seeds; as the Syriac and Arabic have it. The Greek is μικρότερον πάντων σπερμάτων, i.e., less than all seeds, meaning very little. This must be understood according to the common usage of speech, by which we call what is very little, or one of very small things, the least; for otherwise to speak precisely, poppy seed, and the seed of rue, and of some other herbs, is less than mustard seed. Thus the preaching of the Gospel by Christ and the Apostles was at first very circumscribed.
2. A grain of mustard seed, especially in Syria, grows into a tree, so that birds dwell—Syriac, build their nests—in its branches. Thus the Gospel grew, and filled the whole world, so that the birds of Heaven, i.e., men lofty in knowledge and understanding as well as kings and princes dwelt in its branches. (See Dan 4:9 and Dan 4:19). Some understand by the birds, the angels, because they have wings, and are very swift. Hear S. Augustine (Serm. 33 de Sanc.). “Peter is a branch; Paul is a branch; blessed Laurence, whose festal day we are celebrating, is a branch. All the Apostles and martyrs of the Saviour are branches; and if anyone will bravely lay hold of them, they will escape being drowned in the waves of the world. He who dwells under their shadow shall not feel the fire of hell, and shall be secure from the storm of the tempest of the devil, and from being burnt up in the day of judgment.”
3. And chiefly by mustard is denoted the igneous force and efficacy of the Gospel. “Pythagoras,” says Pliny (l. 20, c. 22), “considered that mustard holds the chief place amongst those things whose force is borne upward; since there is nothing which more thoroughly penetrates the nose and the brain.” A grain of mustard refers to the fervour of faith, says S. Augustine.
4. Mustard seed must be bruised; for when it is bruised it emits its igneous force and flavour. Thus the preaching of the Gospel was as it were, bruised by a thousand oppressions and persecutions, which the Apostles suffered; and then it breathed forth its igneous force and strength.
5. Mustard seed, as Pliny says, is sharp and biting. It draws tears, purges away phlegm and cerebral secretions; it is masticated for toothache; when bruised and mixed with vinegar it is applied to the stings of scorpions and the bites of snakes; it is an antidote to the poison of fungi; it is beneficial for the breast and lungs; it is useful against epilepsy, dropsy, asthma, lethargy, and many other diseases. Thus the Gospel expels poisons, that is sins, by the emetic of confession; it is sharp and biting, because it teaches penance and the cross; it excites the tears of compunction; it is medicine for all the faculties of the soul, and especially it dries up concupiscence, and animates to virtue. “The bitterness of its words is the medicine of souls,” says S. Augustine.
6. Mustard seed by its sharpness seasons food, and renders it palatable. So also the Gospel renders palatable everything which is hard and difficult by means of the example of Christ, and by the hope of future glory which it promises.
S. Augustine says, “A grain of mustard seed is great, not in appearance, but in virtue. At first appearance it seems small, worthless, despised, not possessing savour, nor odour, nor sweetness; but when it is bruised, it sheds abroad its odour and exhales nourishment of a fiery taste. It is so inflamed with the fervour of heat that there might be enclosed in it so much fire, by which men could (especially in the winter-time) drive away cold, and warm themselves inwardly.” After this he applies the qualities of mustard to the Gospel and the Christian faith, thus: “Thus too the Christian faith, at first sight, appears small and worthless, not manifesting its power, not carrying any semblance of pride, neither furnishing grace. But as soon as it begins to be bruised by divers temptations, immediately it manifests its vigour, it indicates its sharpness, it breathes the warmth of belief in the Lord, and is possessed with so great ardour of divine fire, that both itself is hot and it compels those who participate to be fervent also. As the two disciples said in the Gospel, when the Lord spoke with them after His Passion, “Did not our hearts burn within us by the way, while the Lord Jesus opened to us the Scriptures?” A grain of mustard, then, warms the inward members of our body, but the power of faith burns up the sins of our heart. The one indeed takes away piercing cold; the other expels the devil’s frost of transgressions. A grain of mustard, I say, purges away corporeal humours, but faith puts an end to the flux of lusts. By the one, medicine is gained for the head; but by faith our spiritual Head, Christ the Lord, is often refreshed. Moreover, we enjoy the sacred odour of faith, according to the analogy of mustard seed, as the blessed Apostle saith, “We are a sweet savour of Christ unto God.
Tropologically: All these things may be applied to a faithful soul, and especially to an Apostle, and to a suffering Christian, or to a martyr. Wherefore the Church adapts this parable to S. Laurence, as the Gospel for his festival. As S. Augustine says, in the work already cited, “We may compare the holy martyr Laurence to a grain of mustard seed; for he, being bruised by various sufferings, deserved to become fragrant throughout the whole world by the grace of his martyrdom. He, when he was in the body, was humble, unknown, and held in low estimation; but after he had been bruised, torn, and burnt he diffused the odour of his nobleness in the churches in all the world. Rightly, therefore, is the comparison applied to him. For Laurence, when he suffers, is inflamed. The fervour of its attrition moves the one; Laurence breathes forth fire in his manifold tribulations. Mustard, I say, is cooked in a small vessel; Laurence is roasted on the gridiron by the fiery flame. Blessed Laurence the martyr was burnt outwardly by the flames of the raging tyrant, but he was inflamed inwardly by the far greater fire of the love of Christ.” The Arabians have a proverb—”A grain of pepper is more powerful than many large gourds;” because if it be bruised it emits a fiery force, and makes itself felt in everyone’s nostrils. You may say the same of a grain of mustard. A believer, therefore, should be a grain of pepper or mustard, and breathe everywhere, and upon all, a divine fire, and so pepper all men, and make them like himself, zealous that is, and ardent in the love of God.
Mat 13:33 Another parable he spoke to them: The kingdom of heaven is like to leaven, which a woman took and hid in three measures of meal, until the whole was leavened.
Another parable, &c. This is Christ’s fourth parable, of leaven, by which (as by the former parable) He shows the power and efficacy of the preaching of the Gospel. As S. Chrysostom says, “Like as leaven communicates its own virtue to a great quantity of meal, so shall ye, 0 ye Apostles, transforn the whole world.” S. Chrysostom observes, with regard to the word hid: “Thus also ye, when ye shall be subjected to your persecutors, shall overcome them. And as leaven indeed is buried but not destroyed, but by degrees transforms everything to its own state; so shall it happen with your preaching. Do not ye, therefore, fear because I said, Many troubles shall happen unto you; for by this means shall ye shine, and shall overcome all.” You will ask why Christ compares the Gospel to leaven? I reply, because leaven is a portion of the meal that has become a little sour, which takes place through fermentation. Hear how Pliny describes the manner in which leaven is made (l 18, c. 11): “Now” (because formerly it was made in another way, as he had related a little before) “leaven is made of the meal itself, which is first kneaded before salt is added, after the manner of pottage, and left until it becomes a little sour. Commonly, indeed, they do not warm it, but only make use of what has been kept from the day before. And evidently it is the nature of heat to cause fermentation; as of bodies that are nourished with fermented bread to become stronger. Thus it was, that among our ancestors the greatest healthiness was attributed to the heaviest wheat.”
Again, leaven, although it be small in bulk, with its heat moistens the whole mass of dough; and as it were effects a change in its entire substance. It makes it palatable and digestible, so that it becomes wholesome bread for nourishing, sustaining and strengthening man. In like manner the Gospel by means of a few Apostles, who suffered many tribulations, converts the whole world to itself and makes the heart of each to be warmed with the love of God. The woman who kneads is the Church, or the power and wisdom of God says S. Augustine.
Tropologically: S. Augustine says, “Christ calls love leaven, because it excites to warmth. The woman he calls wisdom. By the three measures of meal we may understand either these three things in man—the whole heart, the whole soul, and the whole mind; or the three degrees of fruit-bearing, an hundred, sixty, and thirty fold; or the three sorts of men, represented by Noah, Daniel and Job.” (l 1. q. q. Evang. q. 12.) Rabanus adds, “He says until the whole was leavened: because charity being hid in our minds ought to grow there until it transmutes the whole mind into its own perfection: that which is begun here, is perfected hereafter.”
S. Ambrose says, that like as leaven is disseminated through the whole mass of the meal, being as it were broken up; “so Christ was broken, torn and dissolved by His various sufferings: and His moisture, that is His precious Blood was poured out for our salvation, that it might by mingling itself with the whole human race, consolidate that race, which lay scattered abroad.” See also S. Chrysostom, who says among other things, “If twelve men leavened nearly all the meal of the world, consider diligently in your minds, how great must be our wickedness and sloth, who, although we are so many, are not able to convert the remnant of the Gentiles, when we ought to be sufficient for a thousand worlds.” S. Boniface, the Apostle of Germany, was wont to weep over the same thing. His was the saying, “That formerly priests of gold celebrated in chalices of wood, but now wooden priests celebrate in golden chalices.”
Three measures: a measure was equal in quality to a bath which is a liquid measure, containing an Italian bushel, or as S. Jerome and Josephus say, a bushel and a half. The measure contained three Attic bushels.
Symbolically: S. Hilary says, the grace of the Gospel was hid in the Law, the Psalms and the Prophets; now it hath appeared in the faith, hope and love of the Holy Trinity, that what the Law constituted, and the Prophets announced, the same might be fulfilled by the advent of the Gospels. Or as others say, that it might be confirmed by the threefold work of God, viz. of creation, redemption and glorification.
Allegorically: S. Bernard, (l. 5. de Consider.) says the Blessed Virgin joined and united in her womb the three natures of Christ, namely soul, body and divinity to the one Hypostasis of the Word.
Mat 13:34 All these things Jesus spoke in parables to the multitudes: and without parables he did not speak to them.
Mat 13:35 That it might be fulfilled which was spoken by the prophet, saying: I will open my mouth in parables, I will utter things hidden from the foundation of the world.
All these things Jesus spoke in parables, meaning in a parabolical manner: things kept secret, Heb. הידות (chidoth), i.e. enigmas, as the Chaldee trans. and S. Jerome (Ps 78:2.). The Arabic has, I will speak things hidden before the foundation of the world. Christ cites the psalm of David, Ps 78:2, who, according to the letter, through the whole psalm, celebrates God’s benefits to the Synagogue, i.e., the people of Israel, from the beginning, i.e. from their going forth out of Egypt under Moses their leader, until David’s own time, in order that he might stir up the people to be grateful to God, and to love and worship Him. But mystically, says S. Jerome, David was there a type of Christ, who celebrates the benefits granted by God through Himself to His Church, and before-time hid. These things were concerning the promised land in heaven, mysteries declared by parables. Observe that the Hebrew word for parables is mashal, which signifies any weighty and famous saying, such a one as predominates over others. For mashal means to rule: thus it came to signify what was obscure and recondite, whether it were an enigma, an allegory, a parable, or a sentence properly so called. Therefore the sentences in that seventy-eighth Psalm are not properly parables, but only weighty sentences. But here there are like weighty sentences and parables properly so called. Thus this verse of the Psalm applies to Christ in both its meanings, but to David only one of them. For in Scripture many things are spoken which are more suitable to the things signified by the allegory, than to the allegory itself and its literal meaning.