Jn 6:60-69
At that time, many of the disciples of Jesus, when they heard it, said, “This is a hard saying; who can listen to it?” But Jesus, knowing in himself that his disciples murmured at it, said to them, “Do you take offense at this? Then what if you were to see the Son of man ascending where he was before? It is the spirit that gives life, the flesh is of no avail; the words that I have spoken to you are spirit and life. But there are some of you that do not believe.” For Jesus knew from the first who those were that did not believe, and who it was that would betray him.