Matthew 13:32

Or; The Lord compares Himself to a grain of mustard seed, sharp to the taste, and the least of all seeds, whose strength is extracted by bruising. This grain then when sown in the field, that is, when seized by the people and delivered to death, and as it were buried in the ground by a sowing of the body, grew up beyond the size of all herbs, and exceeded all the glory of the Prophets. For the preaching of the Prophets was allowed as it were herbs to a sick man; but now the birds of the air lodge in the branches of the tree. By which we understand the Apostles, who put forth of Christ's might, and overshadowing the world with their boughs, are a tree to which the Gentiles flee in hope of life, and having been long tossed by the winds, that is by the spirits of the Devil, may have rest in its branches.

"Another parable put He forth unto them, saying, The Kingdom of Heaven is like to a grain of mustard seed." That is, since He had said, that of the crop three parts are lost, and but one saved, and in the very part again which is saved so great damage ensues; lest they should say, "And who, and how many will be the faithful?" this fear again He removes, by the parable of the mustard seed leading them on to belief, and signifying that in any case the gospel shall be spread abroad. Therefore He brought forward the similitude of this herb, which has a very strong resemblance to the subject in hand; "Which indeed is the least," He saith, "of all seeds, but when it is grown, it is the greatest among herbs, and becometh a tree, so that the birds of the air come and lodge in the branches thereof." Thus He meant to set forth the most decisive sign of its greatness. "Even so then shall it be with respect to the gospel too," saith He. Yea, for His disciples were weakest of all, and least of all; but nevertheless, because of the great power that was in them, it hath been unfolded in every part of the world.

The kingdom of heaven is the preaching of the Gospel, and the knowledge of the Scriptures which leads to life, concerning which it is said to the Jews, The kingdom of God shall be taken from you. (Mat. 21:43.) It is the kingdom of heaven thus understood which is likened to a grain of mustard seed. The man who sows is by most understood to be the Saviour, who sows the seed in the minds of believers; by others the man himself, who sows in his field, that is, in his own heart. Who indeed is he that soweth, but our own mind and understanding, which receiving the grain of preaching, and nurturing it by the dew of faith, makes it to spring up in the field of our own breast? Which is the least of all seeds. The Gospel preaching is the least of all the systems of the schools; at first view it has not even the appearance of truth, announcing a man as God, God put to death, and proclaiming the offence of the cross. Compare this teaching with the dogmas of the Philosophers, with their books, the splendour of their eloquence, the polish of their style, and you will see how the seed of the Gospel is the least of all seeds. For the dogmas of Philosophers when they have grown up, show nothing of life or strength, but watery and insipid they grow into grasses and other greens, which quickly dry up and wither away. Brit the Gospel preaching; though it seem small in its beginning, when sown in the mind of the hearer, or upon the world, comes up not a garden herb, but a tree, so that the birds of the air (which we must suppose to be either the souls of believers or the Powers of God set free from slavery) come and abide in its branches. The branches of the Gospel tree which have grown of the grain of mustard seed, I suppose to signify the various dogmas in which each of the birds (as explained above) takes his rest. Let us then take the wings of the dove, that flying aloft we may dwell in the branches of this tree, and may make ourselves nests of doctrines, and soaring above earthly things may hasten towards heavenly. (Ps. 55:6.)

(Mor. xix. 1.) Christ Himself is the grain of mustard seed, who, planted in the garden of the sepulchre, grew up a great tree; He was a grain of seed when He died, and a tree when He rose again; a grain of seed in the humiliation of the flesh, a tree in the power of His majesty. (ubi sup.) The birds lodge in its branches, when holy souls that raise themselves aloft from thoughts of earth on the wings of the virtues, breathe again from the troubles of this life in their words and comfortings.

And it should be noted that, when He says, Sowed good seed, He intends that good will which is in the elect; when He adds, An enemy came, He intimates that watch should be kept against him; when as the tares grow up, He suffers it patiently, saying, An enemy hath done this, He recommends to us patience; when He says, Lest haply in gathering the tares, &c. He sets us an example of discretion; when He says, Suffer both to grow together till the harvest, He teaches us long-suffering; and, lastly, He inculcates justice, when He says, Bind them into bundles to burn.