“I am the living bread that came down from heaven. If anyone eats of this bread, he will live forever. And the bread that I will give for the life of the world is my flesh.” (John 6:51, ESV)
John’s Gospel indicates that Jesus fed the 5000 with the miraculous multiplication of loaves of bread near the feast of the Passover (6:2). The fact that this miracle took place at Passover meant that this was on the minds of the people. They would have recalled that for 40 years, God fed manna to the Israelites while they wandered in the desert. Manna was the only nourishment they needed.
The day after the miracle, Jesus taught the Jews its significance, making the connection between Himself and Moses. Jesus performed this miracle as a sign to show the people that He was the Messiah, the leader of the new Israel, one like Moses, but greater. Jesus was going to provide them with bread, but the bread that He would give was not literal food. He was going to provide them with the Bread that they needed for eternal life: Himself.
But the Jews did not understand Jesus’ words or the spiritual significance of what He had done and would do. They sought Jesus because they ate and were filled. They saw only the temporal aspects of the miracle, their bellies were filled, and completely missed the spiritual significance. They failed to see that the ultimate purpose of life is not the satisfaction of material needs, but the satisfaction of spiritual need. They saw spirituality in terms of their religion and working to satisfy its traditions and the law. Jesus was talking about faith. The key to eternal life, to living in oneness with God is not works, or being born a Jew or an American or a Lutheran or what have you. The key to eternal life is faith in Jesus.