John Calvin Commentary Matthew 13:34

"All these things spake Jesus in parables unto the multitudes; and without a parable spake he nothing unto them:" — Matthew 13:34 (ASV)

All these things Jesus spoke in parables. Though Mark expressly says that Christ spoke the word to them as they were able to bear it, yet I think it probable that He continued to employ parables, not so much for the purpose of instruction, as to keep the attention of His hearers awake until a more convenient time. For why did He explain them in detail to His disciples when they were apart? Was it because they were slower to understand than the crowd? No; but because He wished to convey to them privately a knowledge of His meaning, and to allow others to remain in a state of suspense, until a more suitable opportunity should arrive. These were only a kind of introduction to the Gospel, the full brightness and proclamation of which was delayed until the proper time.

There is an apparent contradiction between this statement of Matthew and the prediction of Isaiah, which was quoted a little before. But this is easily resolved; for, though He withdrew the light of doctrine from the reprobate, yet this did not prevent Him from accommodating Himself to their capacity, so as to render them inexcusable. He therefore adopted a method of teaching which was proper and suitable to hearers, whom He knew to be not yet sufficiently prepared to receive instruction.