16 “And Jesus said to him.” Now is He, the day, discerning between the light and the darkness. “For judgment am I come into this world; that they who see not might see, and they who see might be made blind.” What is this, Lord? A weighty subject of inquiry have You laid on the weary; but revive our strength that we may be able to understand what You have said. You have come “that they who see not may see:” rightly so, for You are the light: rightly so, for You are the day: rightly so, for Thou deliverest from darkness: this every soul accepts, every one understands. What is this that follows, “And those who see may be made blind?” Shall then, because You have come, those be made blind who saw? Hear what follows, and perhaps you will understand.
Source: Tractates on the Gospel of John (New Advent)