A.T. Robertson Commentary John 9:16

"Some therefore of the Pharisees said, This man is not from God, because he keepeth not the sabbath. But others said, How can a man that is a sinner do such signs? And there was division among them." — John 9:16 (ASV)

Because he keepeth not the sabbath (οτ το σαββατον ου τηρε). This is reason (causal οτ) enough. He violates our rules about the Sabbath and therefore is a Sabbath-breaker as charged when here before (5:10,16,18). Hence he is not "from God" (παρα θεου). So some.

How can a man that is a sinner do such signs? (Πως δυνατα ανθρωπος αμαρτωλος τοιαυτα σημεια ποιειν; ). This was the argument of Nicodemus, himself a Pharisee and one of the Sanhedrin, long ago (3:2). It was a conundrum for the Pharisees. No wonder there was "a division" (σχισμα, schism, split, from σχιζω) as in 7:43; 10:19.