Albert Barnes Commentary John 9:29

"We know that God hath spoken unto Moses: but as for this man, we know not whence he is." — John 9:29 (ASV)

We know, and so on. We know that God commanded Moses to deliver the law. In that, they were correct; but they assumed their interpretation of the law to be infallible, and therefore condemned Jesus.

As for this fellow. The word fellow is not in the original Greek. It is simply "this." The word fellow implies contempt, which cannot be proven they intended to express.

Whence he is. We do not know his origin, his family, or his home. The contrast with the preceding part of the sentence shows that they intended to express their belief that he was not from God. They did not know whether he was mad, whether he was instigated by the devil, or whether he spoke of himself. See John 7:27; John 8:48–52.