Luke 8:4

And therefore it is significantly said, When much people were gathered together, and were come to him out of every city. For not many but few there are who walk the strait road, and find the way which leadeth to life. Hence Matthew says, that He taught without the house by parables, but within the house explained the parable to His disciples. (Matt. 13:36.) (in Prov. 1.) Now a parable is a narration of an action as done, yet not done according to the letter, though it might have been, representing certain things by means of others which are given in the parable. An enigma is a continued story of things which are spoken of as done, and yet have not been done, nor are possible to be done, but contains a concealed meaning, as that which is mentioned in the Book of Judges, that the trees went forth to anoint a king over them. (Judges 9:8.) But it was not literally a fact as is said, A sower went out to sow, like those facts related in history, yet it might have been so.

That which David had foretold in the person of Christ, I will open my mouth in parables, (Ps. 78:2.) the Lord here fulfils; as it is said, And when much people were gathered together, and were come to him out of every city, he spake by a parable. But the Lord speaks by a parable, first indeed that He may make His hearers more attentive. For men were accustomed to exercise their minds on dark sayings, and to despise what was plain; and next, that the unworthy might not receive what was spoken mystically.