John Chrysostom

But the blind man did not yet know Christ, for before he went to Christ he was blind, and after his cure, he was taken hold of by the Jews: He answered and said, Who is He, Lord, that I might believe on Him? The speech this of a longing and enquiring mind. He knows not who He is for whom he had contended so much; a proof to thee of his love of truth. The Lord however says not to him, I am He who healed thee; but uses a middle way of speaking, Thou hast both seen Him.

Catena Aurea by Aquinas ↗

Cyril of Alexandria

The soul furnished with sound reason, diligently seeking the word of truth with the eyes of the understanding free, without embarrassment makes straight for it like a ship going into port, and obtains its advantages by a chase without fatigue. And again the man who had been blind will be a proof of what has been said. …

Commentary on the Gospel of John, Book 6 ↗

Thomas Aquinas

1356 Next he mentions the desire of the man born blind to believe. We have to recall that this man had not yet physically seen Christ: for he had not seen him when Christ anointed his eyes and sent him to the pool of Siloam, and when he wanted to go back to him he was detained by the Pharisees and the Jews. However, although he had not physically seen Jesus, he believed that the one who opened his eyes was the Son of God. …

Commentary on John ↗

Bonaventure

He answered and said: Who is He, Lord, that I may believe in Him? As if to say: I am ready to believe: whence Chrysostom: "This is the word of one who inquires and desires"; therefore he is instructed. The blind man consented to faith.

Commentary on John, Chapter 9 ↗