Matthew 13:3

And having sat down there, He speaks by parables. "And He spake," it says, "many things unto them in parables." And yet on the mount, we know, He did no such thing, neither did He weave His discourse with so many parables, for then there were multitudes only, and a simple people; but here are also Scribes and Pharisees. But do thou mark, I pray thee, what kind of parable He speaks first, and how Matthew puts them in their order. Which then doth He speak first? That which it was most necessary to speak first, that which makes the hearer more attentive. For because He was to discourse unto them in dark sayings, He thoroughly rouses His hearers' mind first by His parable. Therefore also another evangelist saith that He reproved them, because they do not understand; saying, "How knew ye not the parable?" But not for this cause only doth He speak in parables, but that He may also make His discourse more vivid, and fix the memory of it in them more perfectly, and bring the things before their sight. In like manner do the prophets also. What then is the parable? "Behold," saith He, "a sower went forth to sow." Whence went He forth, who is present everywhere, who fills all things? or how went He forth? Not in place, but in condition and dispensation to usward, coming nearer to us by His clothing Himself with flesh. For because we could not enter, our sins fencing us out from the entrance, He comes forth unto us. And wherefore came He forth? to destroy the ground teeming with thorns? to take vengeance upon the husbandmen? By no means; but to till and tend it, and to sow the word of godliness. For by seed here He means His doctrine, and by land, the souls of men, and by the sower, Himself.

And it is to be noted, that He spake not all things to them in parables, but many things, for had He spoken all things in parables, the people would have departed without benefit. He mingles things plain with things dark, that by those things which they understand they may be incited to get knowledge of the things they understand not. The multitude also is not of one opinion, but of divers wills in divers matters, whence He speaks to them in many parables, that each according to their several dispositions may receive some portion of His teaching.

By this sower is typified the Son of God, who sows among the people the word of the Father. Or, He was within while He was yet in the house, and spake sacraments to His disciples. He went therefore forth from the house, that He might sow seed among the multitudes. Note that this is the first parable that has been given with its interpretation, and we must beware where the Lord expounds His own teachings, that we do not presume to understand any thing either more or less, or any way otherwise than as so expounded by Him.