John 6:70 Commentary and Bible Study

The Twelve are indeed stable and will not turn away from him as the crowds have done, but the explanation for this is not their inherent loyalty and faith. Rather it is that God has chosen them from all eternity, worked secretly in their hearts, and called them for this very hour so that they could follow Christ and learn of him, and be witnesses to the resurrection, and take the gospel into all world in obedience to their risen Lord. Therefore we cannot take credit for their loyalty to Christ while others turn back, but they must instead give glory to God that he has chosen then and kept them. Yet among even them, there is one horrifying individual who will in fulfilment of prophecy do something which might fill the rest with fear. For them to be told that one of their number was a devil was to set all the Twelve on their guard, for although he is named by John in the next verse, he was not known to the other eleven until the night of the betrayal of Christ.