John Chrysostom
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.
Seeing the Lord had said above that three parts of the seed perish, and one only is preserved, and of that one part there is much loss by reason of the tares that are sown upon it; that none might say, Who then and how many shall they be that believe; He removes this cause of fear by the parable of the mustard seed: therefore it is said, Another parable put he forth unto them, saying, The kingdom of heaven is like unto a grain of mustard seed.