I am the living bread that came down from heaven; whoever eats this bread will live forever; and the bread that I will give is my flesh for the life of the world." The Jews quarreled among themselves, saying, "How can this man give us (his) flesh to eat?" Jesus said to them, "Amen, amen, I say to you, unless you eat the flesh of the Son of Man and drink his blood, you do not have life within you. Whoever eats my flesh and drinks my blood has eternal life, and I will raise him on the last day. For my flesh is true food, and my blood is true drink. Whoever eats my flesh and drinks my blood remains in me and I in him. Just as the living Father sent me and I have life because of the Father, so also the one who feeds on me will have life because of me. This is the bread that came down from heaven. Unlike your ancestors who ate and still died, whoever eats this bread will live forever." (Jn 6:51-58)
Jesus starts his argument saying that he is the bread that has come down from heaven. From where the bread comes is more important. Jews have already argued saying that Moses gave bread in the wilderness. But here it is the father who gives the bread. Jesus is arguing about his origin. He says that he is from the father and he has come down from the father.
Father is in the heaven and he has sent the son from heaven and hence anything to do with the son will in turn take the people to where he has come down from. Whoever eats the son (who has come down from heaven) will have the same effect. They will in turn reach heaven. Jesus argument is regarding his arrival from and his journey to.
Jesus abiding presence is with those who eat his body and drink his blood. (Whoever eats my flesh and drinks my blood remains in me and I in him. Just as the living Father sent me and I have life because of the Father, so also the one who feeds on me will have life because of me). Indwelling of Jesus helps the believer to be in union with the father. And that is eternal life.
