The religious leaders frequently asked Jesus to prove to them why he was better than the prophets they already had. Jesus here referred to the manna that Moses had given their ancestors in the desert (Ex. 16). This bread was physical and temporal. The people ate it, and sustained them for a day. But they had to get more bread every day, and this bread could not keep them from dying. Jesus, who is much greater than Moses, offers himself as the spiritual bread from heaven that satisfies completely and leads to eternal life.
How can Jesus give us his flesh as bread to eat? To eat living bread means to accept Christ into our lives and become united with him. We are united with Christ in two ways: (1) believing in his death ( the sacrifice of his flesh) and resurrection and (2) by devoting ourselves to living as he requires, depending on his teaching for guidance, and trusting in the Holy Spirit for power.
God, not man, plays the most active role in salvation. When someone chooses to believe in Jesus Christ as Savior, he or she does so only in response to the urging of God's Holy Spirit. God does the urging; then we decide whether or not to believe. This no one can believe in Jesus without God's help.
Some of the people grumbled in disagreement because they could not accept Jesus claim of divinity. They saw him only as a caroenter from Nazareth. They refused to believe that Jesus was God's divine Son, and they could not tolerate his message. Many people reject Christ because they say they cannot believe he is the Son of God. In reality, the demands that Christ makes for their loyalty and obedience are what they can't accept. So to protect themselves from the message, they reject the messenger.
Jesus was alluding to an Old Testament view of the Messianic kingdom in which all people are taught directly by God (lsa. 54:13; Jer. 31:31-34). He was stressing the importance of not merely hearing, but learning. We are taught by God through the Bible, our experiences, the thoughts the Holy Spirit brings, and relationships with other Christians. Are you open to God's teaching?
This was a shocking message, to eat flesh and drink blood sounded cannibalistic. The idea of drinking any blood, let alone human blood, was repugnant to the religious leaders because the law forbade it (Lev. 17:10, 11). Jesus was not talking about literal blood, of course. He was saying tgat his life had to become their own, but they could not accept this concept. The Gospel writers, as well as the apostle Paul, used the body and blood imagery in talking about communion ( 1 Cor. 11:23-26)