You have heard today, brethren, how the whole magnitude of the heavenly kingdom is compared to a grain of mustard. And what is it that so small, so least—nay, the least of the least—a likeness encloses so great a power? For thus says the Lord: 'To what is the kingdom of God like? and to what shall I esteem it like?' (Luke 13). When he says, 'To what is it like,' he indicates and draws forth, as it were, the affection of one seeking. And does he alone—the Word, the fount of knowledge, the river of speech, who waters the hearts of all, opens the senses, dilates the wit—now labor in finding a likeness? But let us hear what he has found. 'It is like,' he says, 'the kingdom of heaven to a grain of mustard.' Seeking in heaven and on earth, he found nothing but a grain of mustard, in which to enclose the whole power of the supernal dominion;
and does that kingdom, powerful in singularity, happy in eternity, resplendent in divinity, diffused throughout the whole heaven, dilated over the whole earth, confine and enclose itself in the narrow limits of a grain of mustard? 'The kingdom of heaven is like a grain of mustard.' Is this the whole hope of believers? Is this the highest expectation of the faithful? Is this the happiness of virgins procured by the long labors of continence? Is this the glory of martyrs won by the whole pouring out of blood? Is this that which neither eye has seen, nor ear heard, nor has it ascended into the heart of man (1 Cor. 2)? Is this that which by an ineffable mystery the Apostle promises to be prepared for those who love God? Brethren, let us not easily be disturbed at the Lord's sayings; for if the weak thing of God is stronger than men;
and the foolish thing of God is wiser than men (1 Cor. 1), this least thing of God is found more magnificent than the whole magnitude of the world; if only we so sow this grain of mustard in our minds, that it may grow into a great tree of understanding for us, and that our sense may be lifted up with all its height to heaven, and be diffused into all the branches of knowledge, and so kindle our fervent mouths with the living savor of its fruit, and so burn wholly for us with the fire of its seed, and be inflamed in the breast, and by its tasting take away from us the whole loathing of our ignorance. 'The kingdom of heaven is like a grain of mustard, which a man took and cast into his garden, and it grew, and became a great tree, and the birds of heaven rested in its branches.'
The kingdom of God, as he says, is like a grain of mustard: it is brought down from above by the word, received by hearing, sown by faith, rooted by belief, grows by hope, is spread abroad by confession, is stretched out by power, and widens into branches, to which it calls the birds of heaven — that is, spiritual understandings — and receives them within itself in a peaceful dwelling. Let the heretic come, let him come, for the entrance of the Church always lies open to those who return; let him come, let him hear, and let him at last cease to bark against the Lord's tender mercy.
If the whole majesty of the heavenly kingdom comes down to the likeness of a grain of mustard, why is it questioned that God descended to man, the Lord into the form of a servant? For thus he came, O heretic, that through faith the whole might grow for you, for whom by nature the whole had already failed. The kingdom of heaven is like a grain of mustard.
But let us return to the grain of mustard: thus the whole sum of the kingdom abides and stands in the kingdom of heaven. Christ is the kingdom of heaven, who, like a grain of mustard cast into the garden of a virginal body, grew into a tree upon the cross over the whole world, and, when ground by his Passion, gave forth so great a savour of his fruit that whatever is living he seasoned and made fragrant by his touch. For just as in the whole grain of mustard its power lies hidden, but its power appears most vehemently if it be ground, so Christ willed to be ground in body, he who did not wish his power to remain concealed. And let us, brethren, grind this grain of mustard, that we may perceive its force in this likeness.
Christ is King, because he himself is the whole origin of reigning; Christ is the kingdom, because in him is the whole majesty of his kingdom; Christ is man, because the whole man is restored in Christ; Christ is the grain of mustard, whence the whole greatness of God is diminished into the whole littleness of man. And what more? He himself became all things, that in himself he might restore all. Christ as man received the grain of mustard, that is, Christ the man received the kingdom of God which Christ the God had always possessed; and he sent it into his own garden, that is, into the Church his bride. Of this garden he often makes mention in the Song of Songs, saying: 'A garden enclosed' (Cant. iv).
The Church is a garden, spread by the ploughshare of the Gospel through the whole world in cultivation, enclosed by the goads of discipline, purged by apostolic labour of every worst weed, made pleasant with the nurseries of the faithful, the lilies of virgins, the roses of martyrs, the verdure of confessors, fragrant with everlasting flowers. This grain of mustard, then, Christ sent into his own garden, that is, in the promise of his kingdom, which was rooted in the patriarchs, born in the prophets, grew in the apostles, in the Church became a great tree, and gave manifold branches in gifts, which the Apostle enumerates, saying:
'To one is given the word of wisdom, to another the word of knowledge, to another the healing of sicknesses, to another the working of miracles, to another prophecy, to another the discernment of spirits, to another kinds of tongues' (1 Cor. xii). You have heard, brethren, into what a tree this grain of mustard has burst forth; you have heard what roots it has founded; you have heard how great and how many branches it has already spread and sown itself into, in which the birds — of heaven, not of the air — may rest by the wings of wisdom and prudence, by their flight, in the security of faith. And you too, hear: if you wish not to fear the earthly beasts, if you wish to escape the birds of prey, the ravenous vultures — that is, the birds of the air, which are all the spiritual wickednesses — lift yourself from the earth, forsake earthly things: take the silvered wings of the prophetic dove (Ps.
lxvii); take the wings radiant with the splendour of the divine Sun, fly forth in the appearance of gold, that upon such great and such branches you may rest for ever, tempted by no snares, strong in such a flight, secure in so great a dwelling. Of the following likeness, with the following word, we shall expound, the Lord teaching us.