A.T. Robertson Commentary John 6:70

"Jesus answered them, Did not I choose you the twelve, and one of you is a devil?" — John 6:70 (ASV)

And one of you is a devil (κα εξ υμων εις διαβολος εστιν). Jesus does not say that Judas was a devil when he chose him, but that he is one now. In 13:2,27 John speaks of the devil entering Judas. How soon the plan to betray Jesus first entered the heart of Judas we do not know (12:4). One wonders if the words of Jesus here did not cut Judas to the quick.