"60 When many of his disciples heard it, they said, “This is a hard saying; who can listen to it?” 61 But Jesus, knowing in himself that his disciples were grumbling about this, said to them, “Do you take offence at this? 62 Then what if you were to see the Son of Man ascending to where he was before?63 It is the Spirit who gives life; the flesh is no help at all. The words that I have spoken to you are spirit and life. 64 But there are some of you who do not believe.” (For Jesus knew from the beginning who those were who did not believe, and who it was who would betray him.) 65 And he said, “This is why I told you that no one can come to me unless it is granted him by the Father.”
66 After this many of his disciples turned back and no longer walked with him. 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.” 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."
John 6:60-71
But now the other reaction Peter's (68). To appreciate the full force of his words we need to look ahead into the history of Acts. It is there that we see how he and his companions really embraced Jesus' words. They were weaned from their earth-bound existence, to prove the reality and the fullness of the hidden manna. They were men who had entered into fellowship with Christ in His death. What do we suppose was the explanation of the mighty character-formation in the lives of believers in the early Church? It is just that they were feeding on the death of Christ and drawing eternal virtue from His atoning sacrifice to make them strong. What riches are to be found in this wonderful paradox of death and life. This is the living bread, and no man will ever hunger spiritually when he is feeding there. Above all, they were in fellowship with Him. He was the centre of their lives; they walked with Him day by day, and they knew the power of that transforming friendship. Here, then, are the alternatives: 'This is a hard saying' or 'Thou hast the words of eternal life'. This is the issue of discipleship; and in this costly and agonising paradox all the greatest and most fruitful experiences of grace lie. Have we not found it so?