John Chrysostom

"Jesus saith unto him, Thou hast both seen Him, and it is He that talketh with thee." He said not "I am He," but as yet in an intermediate and reserved manner, "Thou hast both seen Him." This was still uncertain; therefore He addeth more clearly, "It is He that talketh with thee."

Homily on the Gospel of John 59 ↗

Cyril of Alexandria

Being asked upon whom it was proper to believe, Jesus points to Himself, and not simply by saying "It is I," but by saying that the Person Whom the other was looking at and by Whom he was being addressed, was the Son of God; in every way consulting beforehand our advantage, and in divers manners constructing aids towards a faith both free from error and unperverted, lest while thinking ourselves pious we might fall into the meshes of the net of the devil, by foolishly turning aside from the truth of the mystery. …

Commentary on the Gospel of John, Book 6 ↗

Theophylact of Ohrid

Jesus answers: "He is the One whom you have seen and who is speaking with you." He did not say "It is I who healed you, who told you: go, wash," but speaks first in a veiled and unclear way, "you have seen Him," and then more clearly, "and He is speaking with you." The Lord, it seems, said "you have seen Him" intentionally, precisely in order to remind him of his healing and of the fact that he received the ability to see from Him.

Commentary on John ↗

Thomas Aquinas

1357 Because, as we read in Wisdom (6:16), "She," that is, Wisdom, "goes about seeking those worthy of her," Christ reveals himself to the man born blind, who desired her, when he says, You have seen him, and it is he who speaks to you. Here Christ is giving him a teaching of faith. First, he mentions the gift he received, saying you have seen him, that is, you, who did not see before, have now seen him. …

Commentary on John ↗

Bonaventure

Jesus said to him: You have both seen Him, and it is He who speaks with you. You have seen Him, through the miraculous work: He speaks with you, through wondrous instruction: above in chapter eight, "I am the Beginning, who also speak to you." In a similar manner the Lord instructed the Samaritan woman above in chapter four: "I am He, who speaks with you." And because "with the heart one believes unto justice, but with the mouth confession is made unto salvation"; therefore there follows the true confession of the enlightened blind …

Commentary on John, Chapter 9 ↗