The Jews murmured about Jesus because he said, “I am the bread that came down from heaven, ” and they said, “Is this not Jesus, the son of Joseph? Do we not know his father and mother? Then how can he say, ‘I have come down from heaven’?”
Jesus answered and said to them, “Stop murmuring among yourselves. No one can come to me unless the Father who sent me draw him, and I will raise him on the last day.
It is written in the prophets: They shall all be taught by God. Everyone who listens to my Father and learns from him comes to me. Not that anyone has seen the Father except the one who is from God; he has seen the Father.
Amen, amen, I say to you, whoever believes has eternal life.
I am the bread of life. Your ancestors ate the manna in the desert, but they died; this is the bread that comes down from heaven so that one may eat it and not die. 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.”
John 6:41-51
Only in Jesus can we find life. He is the Bread of Life and give us his flesh to sustain us. Many people who had been following him found this teaching too difficult and left him after this discourse. He is preparing them for the gift of the Eucharist, which some cannot accept.