15 But, as I have already said before, brethren, when they expel, the Lord receives; for the rather that he was expelled, was he made a Christian. “Jesus heard that they had cast him out; and when He had found him, He said unto him, Do you believe in the Son of God?” Now He washes the face of his heart. “He answered and said,” as one still only anointed, “Who is he, Lord, that I might believe in him? And Jesus said unto him, You have both seen Him, and it is He that talks with you.” The One is He that is sent; the other is one washing his face in Siloam, which is interpreted, Sent. And now at last, with the face of his heart washed, and a conscience purified, acknowledging Him not only as the son of man, which he had believed before, but now as the Son of God, who had assumed our flesh, “he said, Lord, I believe.” It is but little to say, “I believe:” would you also see what he believes Him? “He fell down and worshipped Him.”
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)