John 6:60-64

Therefore many of His disciples, when they heard this, said, “This is a hard saying; who can understand it?” When Jesus knew in Himself that His disciples complained about this, He said to them, “Does this offend you? What then if you should see the Son of Man ascend where He was before? It is the Spirit who gives life; the flesh profits nothing. The words that I speak to you are spirit, and they are life. But there are some of you who do not believe.” For Jesus knew from the beginning who they were who did not believe, and who would betray Him.