(John 6:66 ESV) 66 After this many of his disciples turned back and no longer walked with him.
The traditional interpretation is that the disciples left Jesus because they thought he was teaching cannibalism or some such thing. And to English-hearing ears, it surely sounds like that.
But that fails to credit the audience in Capernaum with knowing how to think in symbolic terms, and it fails to credit Jesus with being able to know his audience well enough to be understood.
Remember that Jews often ask questions in response to questions. In the culture of the day, the way to get a speaker to go deeper or explain himself is to ask a question, even an obtuse-sounding question. We’ve seen this very behavior with Nicodemus, the Samaritan woman, and the audience in Capernaum. (What? You didn’t think you’d enjoy this link? “A rabbi once said: ‘We are closer to God when we are asking questions than when we think we have the answers.'”)
Of course, they asked how Jesus could say that they must eat his flesh. But not necessarily because they were thinking in terms of cannibalism. If they got the image, then they’d have to wonder about the fact that Jesus is very much alive and this is the language of sacrifice. You eat the flesh of lamb given at the Temple —
(Lev 7:15 ESV) 15 And the flesh of the sacrifice of his peace offerings for thanksgiving shall be eaten on the day of his offering. He shall not leave any of it until the morning.
(Lev 8:31 ESV) 31 And Moses said to Aaron and his sons, “Boil the flesh at the entrance of the tent of meeting, and there eat it and the bread that is in the basket of ordination offerings, as I commanded, saying, ‘Aaron and his sons shall eat it.’
Jesus is using the language of Leviticus to speak of eating a sacrifice, and yet he is plainly alive and well. The missing piece is Jesus’ death. And so Jesus is implying his death (and he very much was), then to eat his sacrificed flesh would be to share in his sacrifice — and that implies martyrdom — which is hard.
Doesn’t that make better sense than imagining the Jews in the synagogue at Capernaum debating cannibalism?
(John 6:67-69 ESV) 67 So Jesus said to the Twelve, “Do you want to go away as well?” 68 Simon Peter answered him, “Lord, to whom shall we go? You have the words of eternal life, 69 and we have believed, and have come to know, that you are the Holy One of God.”
It’s a poignant moment. Jesus was concerned that many were leaving him. But Jesus does not avoid the hard question. He goes straight to the point and asks his disciples if they’ll stick with him.
Peter (of course, it was Peter) expresses the faith of the group. “You have the words of eternal life.” Peter understood that Jesus was speaking of eternal life, and therefore about the resurrection.
“Holy One” refers to such passages as —
(Psa 16:10 ESV) 10 For you will not abandon my soul to Sheol, or let your holy one see corruption.
But the term is normally used in the Old Testament to refer to God. This is quite a declaration of faith!
(John 6:70-71 ESV) 70 Jesus answered them, “Did I not choose you, the Twelve? And yet one of you is a devil.” 71 He spoke of Judas the son of Simon Iscariot, for he, one of the Twelve, was going to betray him.
This portends Jesus’ betrayal, and lets us know that Jesus well knew the hearts of his followers. And yet it seems an odd time and place for Jesus to say such a thing.
Perhaps the point Jesus is making is that even when he chooses someone (the same verb as in Eph 1:4), they remain who they are and make the choices they wish to make.
Just as Jesus could not keep many of his disciples from leaving him — and you can surely hear the disappointment in his words — he cannot keep Judas from being Judas. He sees the limits of his ability to persuade, and he is saddened that many will not come to belief despite miracles and sermons and all the lovingkindness of God Almighty.