Jesus answers Peter's warm confession with a sober warning. Peter had said "we believe and are sure" for all twelve (John 6:69), and Gill notes that Peter "had now no suspicion of Judas." Jesus knew more. John had already said that Jesus "knew from the beginning" who would betray Him (John 6:64).

The question has two halves. The first presses the privilege of the twelve: Jesus Himself chose them. Barnes hears much emphasis here: "I, the Saviour, the Messiah, chosen you in mercy and in love, and therefore it will be a greater sin to betray me." The second half exposes that one among the chosen was an enemy. Gill clarifies that the choosing here was to be apostles, "not to grace and glory," though that was true of the other eleven.

The text records no reply from the twelve. John explains the words for the reader: "He spake of Judas Iscariot the son of Simon: for he it was that should betray him, being one of the twelve" (John 6:71). Jesus did not name Judas to the group. The full meaning came out at the last supper, when "the devil" put betrayal into Judas's heart and "Satan entered into him" (John 13:2, 27).

In the Greek, Jesus includes the pronoun ego, "I," which Greek verbs do not need. The interlinear reads, "Not I you the twelve did choose?" Barnes notes the emphasis of "Have not I." The verb is exelexamen, "I chose," the same act Luke describes when Jesus chose twelve "whom also he named apostles" (Luke 6:13).

The word for devil is diabolos. Barnes explains that it is used here "in the sense of an enemy, or one hostile to him," one with "the spirit, the envy, the malice, and the treasonable designs of a devil." Gill says Judas was like the devil, "a deceiver, a liar, and a murderer." Judas's father is named Simon (John 6:71), a different man from Simon Peter.

This question shows that Jesus is never deceived. He chose the twelve knowing exactly who they were. Later He would say, "I know whom I have chosen: but that the scripture may be fulfilled" (John 13:18), and in prayer He would say none was lost "but the son of perdition" (John 17:12). Judas's betrayal did not take Jesus by surprise or defeat His plan.

Matthew Henry is blunt: "Judas not only had a devil, but he was a devil," and "hypocrites and betrayers of Christ are no better than devils." Yet Jesus chose Judas, counted him among the twelve, and warned the group. The warning comes right after a true confession; Barnes reads it as Jesus cautioning Peter "not to be too confident."