John 6:67-71 — Then said Jesus unto the twelve, Will ye also go away?
Then Simon Peter answered Him, Lord, to whom shall we go? Thou hast the words of eternal life.
And we believe and are sure that Thou art that Christ, the Son of the living God.
Jesus answered them, Have not I chosen you twelve, and one of you is a devil?
He spake of Judas Iscariot the son of Simon: for he it was that should betray Him, being one of the twelve.
Christ knew what they would do. Why ask? To test them? To hear them state their faith? In Greek, this question expects a negative answer. Jesus knew their hearts.
Peter, always the first to speak out, sometimes in rashness and ignorance, but sometimes, like here, in earnestness and faith.
We believe and we are sure — In Greek, the tense indicates an ongoing, abiding faith.
The crowd had been attracted by Christ's miracles, but Peter speaks of His words (verse 68) See verse 63.
Verse 69 — literally, "the Holy One of God"
Verse 71 — John knew of Judas' betrayal when he wrote this, but not at the time.
devil — sold out to Satan (John 13:2, 27).
So why did Christ choose Judas? Yea, Mine own familiar friend, in whom I trusted, which did eat of My bread, hath lifted up his heel against Me (Psalm 41:9). While I was with them in the world, I kept them in Thy name: those that Thou gavest Me I have kept, and none of them is lost, but the son of perdition; that the scripture might be fulfilled (John 17:12).
Judas, who spent three years with Christ and never believed still couldn't find any flaws in Him. I have sinned in that I have betrayed the innocent blood (Matthew 27:4).