John Chrysostom

"What man is that which said unto thee, Take up thy bed and walk? And he that was healed wist not who it was: for Jesus had conveyed Himself away, a multitude being in that place." And why did Jesus conceal Himself? First, that while He was absent, the testimony of the man might be unsuspected, for he who now felt himself whole was a credible witness of the benefit. …

Homily on the Gospel of John 37 ↗

Theophylact of Ohrid

The Jews do not ask him, "Who healed you?" but rather, "Who told you to take up your bed?" Thus they willingly shut their eyes to the good, while constantly bringing the supposed violation of the Sabbath to the forefront.

Commentary on John ↗

Augustine of Hippo

And he, in defence, put the author of his healing before his censors, saying, "He that made me whole, the same said unto me, Take up thy bed, and walk." Should I not take injunction from him from whom I received healing? And they said, "Who is the man that said unto thee, Take up thy bed, and walk?"

Tractates on John 17 ↗

Thomas Aquinas

Then, since they could not very well charge the man who was cured, they try to belittle Christ's cure, for this man defended himself through Christ. But since he did not indicate precisely who he was, they maliciously ask him who it was. With respect to this, first, the search for Christ is set down. Secondly, his discovery. And thirdly, his persecution (v 16). Three things are mentioned about the first: the Jews' interrogation; the ignorance of the man who was cured, and the cause of that ignorance. …

Commentary on John ↗

Bonaventure

"They therefore asked him: Who is that man," a weak man, not God almighty, "who said to you: Take up your bed and walk?" who commanded against the Law, not who healed by power. They seek evil things, they are silent about good things: Proverbs 11: "He who seeks good things rises well at dawn: the searcher of evils shall be oppressed by them." And because they seek with evil intent, therefore they fail in their inquiry.

Commentary on John, Chapter 5 ↗