St John's Gospel, chapter six, is about the Eucharist.
Jesus talked to the crowd.
First, Jesus used the miracle of the loaves to teach about the everlasting bread. Second, Jesus used the visible image, the bread that did not last, to talk about the invisible bread, the everlasting bread v.27.
Third, Jesus revealed the living bread, the everlasting bread, which was nothing else, but of His own Body and Blood v.35.
At this point, the crowd, and some of Jesus' disciples went home unhappy. They followed Jesus not to hear the truth, but with their own agenda, and when their expectation was not met, they left Jesus.
Their agenda was, that Jesus would lead them to overthrow the Roman Empire. This political view was what they accused Jesus of at His trial.
Second, some believed Jesus was not God, but simply a great prophet, who could perform miracles and healings.
Third, the heart of the problem was not much about understanding Jesus' teaching, but rather about their hope that was not met. This problem remains in today's world. People do not 'Let God be God'. They want to have a god compatible to 'their' god, whom they have already formed in their own heads. Jesus revealed the reality of God. The people of His day rejected this. They would not accept the God-Incarnate, Who lived among them.
The mystery of the Eucharist is the ultimate sacrifice, Jesus, out of His love, gave to His followers. This mystery is not for us to understand, but to believe. God, the Father told us to listen to Jesus when He said:
'This is my Son, the Chosen One, listen to him'. Lk 9,35.
We are called, not to understand, but to listen, and to believe what Jesus taught. 'Listen to Him' to know what we have never heard, that what looks like normal bread and wine on the Altar, after the consecration, are truly the Body and Blood of Jesus. Faith simply is about understanding what the Divine allows us to understand, and to believe, what the Divine calls us to believe. Jesus revealed the mystery of the Eucharist for us to believe, that a/ God loves us; b/ God gives us life; c/ God is near to us; d/ God lives amongst us; and e/ finally God gives us eternal life.
Lord, who shall we go to? You have the message of eternal life'. v.68.
Peter confessed, that those who refused the true God Jesus offered, would turn to an idol god. The God, that Jesus revealed, had the true message of eternal life.
Jesus knew His teaching about the real presence was not simple. It required faith to believe. It was not an ordinary faith, but the faith which came from the Father. Jesus became one of us. He used our human language to talk about divine love. Jesus told us. 'It is the spirit that gives life, the flesh has nothing to offer. The words I have spoken to you are spirit and they are life' v.63. The 'flesh' Jesus talked about was not about ours, but of His own 'flesh'. 'The Word was made 'flesh', he lives among us' Jn 1,14. The crowds failed to understand this teaching. They believed Jesus was an ordinary man, who came from their village.
We give thanks to Jesus for becoming one of us, so we can learn from Him.