John Calvin on Matthew 13:13

13. For this reason I speak by parables. He says that he speaks to the multitude in an obscure manner, because they are not partakers of the true light. And yet, while he declares that a veil is spread over the blind, that they may remain in their darkness, he does not ascribe the blame of this to themselves, but takes occasion to commend more highly the grace bestowed on the Apostles, because it is not equally communicated to all. He assigns no cause for it, except the secret purpose of God; for which, as we shall afterwards see more fully, there is a good reason, though it has been concealed from us. It is not the only design of a parable to state, in an obscure manner, what God is not pleased to reveal clearly; but we have said that the parable now under our consideration was delivered by Christ, in order that the form of an allegory might present a doubtful riddle.