Our Lord Jesus was so "in your face". To the flesh, His words conjure up a gruesome picture. But to the Spirit born mind and heart, these are wonderful, soul nourishing truths. In Hebrews 10:5, Jesus is prophetically saying to the Father, "but a body You have prepared for me." This is from Psalm 40:6-8 where the words are "I delight to do thy will O God." Is this a discrepancy? Not at all. The Holy Spirit is teaching us that God gave Jesus a body of perfect obedience to the Father's will, unlike fallen man's defiled and stubborn will that could not do the Father's Will embodied in the Law. "Then He said, Behold, I have come to do Your Will, O God. He takes away the first covenant that He may establish the second. By that Will we have been sanctified through the offering of the body of Jesus Christ once for all." (Heb 10:9-10) Our Jesus' body is the only human body that did and does the will of God perfectly and satisfactory. His body is our only hope of being sanctified--being set apart unto God.
Back to John 6:53-57. How are these passages related? Jesus is exhorting us to feast on His perfectly obedient body. His is the only satisfactory obedience that we can offer to the Father. But how do we feast on Him? Jesus language is so distasteful at first glance--"eat my flesh and drink my blood." But he has already told us previously in the chapter what He means. "Moses did not give you the bread from heaven, but My Father gives you the true Bread from heaven. For the bread of God is He who comes down from heaven and gives life to the world.........I am the bread of life. He who COMES TO ME SHALL NEVER HUNGER, AND HE WHO BELIEVES IN ME SHALL NEVER THIRST." John 6:32-35 Feasting on Jesus is coming continually by faith, and drinking His blood is a continual believing on Him. Do not mistake these for separate actions. "The Just shall live by faith." Romans 1:18--in what? We live by the faith that God has given us a Man, a God/Man in whom the Father is perfectly pleased! (Matt. 3:17, 17:5) He is the Man our faith and hope rests in. He is our acceptance before the Father. (Ephesians 1:6) He is our ONLY righteousness. (I Corinthians 1:30, II Corinthians 5:21, Romans 3:21-23. And as Colossians 2:10a says, "for in Him dwells all the fullness of the Godhead BODILY, AND YOU ARE COMPLETE IN HIM." All of our incompleteness, our inadequacies, our failures, yes, all our plain old sin--all find their answer in the perfect God/Man. He alone is the Father's Pleasure--Hear Him!