Jerome
Catena Aurea · Matthäusevangelium 13
Another parable put he forth unto them, saying, The kingdom of heaven is like to a grain of mustard seed, which, a man took, and sowed in his field: Which indeed is the least 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.
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.