“There is no wickedness, indeed, that is perpetrated by men, to which Satan does not excite them, but the more hideous and execrable any crime is, the more ought we to view in it the rage of the devil, who drives about, in all possible directions, men who have been forsaken by God. But though the lust of men is kindled into a fiercer flame by Satan’s fan, still it does not cease to be a furnace; it contains the flame kindled within itself, it receives with avidity the agitation of the fan, so that no excuse is left for wicked men.”
John Calvin Calvin’s Commentaries, Volume 7: The Gospels (Grand Rapids: Associated Publishers and Authors Inc., n.d.), p. 821.
"Judas is a prime example of a professing believer who fell into absolute apostasy. For three years he followed the Lord with the other disciples. He appeared to be one of them. Presumably he thought of himself as a believer, at least at the outset. It is doubtful that he joined Christ's band with the intention of turning against him. Somewhere along the line he became greedy, but that could hardly have been his motive in the beginning; Jesus and the disciples never had anything of material value (Matthew 8:20). Apparently Judas initially shared the hope of Christ's kingdom, and he likely believed that Jesus was the Messiah. After all, he also had left everything to follow the Lord. In modern terminology, he had 'accepted' Jesus ...."
"Yet, while the others were growing into apostles, Judas was quietly becoming a vile, calculating tool of Satan. Whatever his character seemed to be at the beginning, his faith was not real (John 13:10-11). He was unregenerated, and his heart gradually hardened so that he became the treacherous man who sold the Savior for a fistful of coins. In the end, he was so prepared to do Satan's bidding that the devil himself possessed Judas (John 13:27)"
John MacArthur The Gospel According To Jesus (1989), p.99