The crowds want Jesus to be their King so He can provide for their daily lives. Jesus has so much more He wants to give them. He shows this by talking about the manna God gave the Israelites in the wilderness. Sure, the manna sustained them day by day. However, it eventually failed them, and every one of them finally died. Jesus wants to give something far greater than manna. He wants to give us Himself-the true Bread from heaven that allows a person to eat and live forever.
That was more than the crowds were willing to accept. They were offended when He said His flesh was that bread. Jesus knew they were upset. Yet rather than backing off, He turned up the heat and pushed even harder, "Truly, truly I say to you, unless you eat the flesh of the Son of Man and drink His blood, you have no life in you." Many in the crowds rejected His terms, turned away and stopped following Him.
What do you think Jesus did? Do you picture Him running after them, calling them back? Not the King of Israel, He stands firm as the multitudes walk away into the darkness. In time even more will abandon Him. Soon He will hang alone on the cross in the darkness, but He will stand firm to the end to save us.
Every human who encounters the King of kings through the Gospel reaches this fork in the road. Repent and believe in Jesus and you will live with Him in heaven forever. Turn away in unbelief and you will die forever.