“And while they were eating he said, ‘I tell you the truth, one of you will betray me.’ They became greatly distressed and each one began to say to him, ‘Surely not I, Lord?'”
Jesus announced ahead of time what would happen to him, so that the disciples might prepare and might know that it was God’s plan. They remained clueless, however.
Instead of self-examination, the disciples reacted in a knee-jerk fashion when Jesus said one of them would betray him and denied that any of them would do it. Let Bible warnings cause us to examine our hearts and motives.