The crowds followed Jesus because they had been fed so marvellously. Jesus fed them with a 'fish sandwich' - two fish and five loaves. It was an ordinary food necessary for physical nourishment. Food that is good for our physical body cannot satisfy our spiritual body. The soul needs a special kind of food that the world cannot offer. We fill ourselves with the food the world provides as nourishment and yet we will still hunger. Jesus insists that He is the real basis of our survival. Only faith in Jesus can satisfy our deepest hungers and we will not be able to survive apart from Jesus. Our survival is in God's hands, not ours.
Work for food that endures to eternal life, the kind of food the Son of Man is offering you, for on him the Father, God himself, has set his seal. v 27
They asked Jesus..
What must we do if we are to do the works that God wants? v 28
The only 'work' required is the work to believe in the person of Jesus. God is sending down from heaven the Bread of Life that is the Imperishable Bread.
The crowds failed to understand the deeper reality: Jesus is really the source of life. He is the bread of life that comes from heaven. To help them capture this reality Jesus told them openly that…
I am the bread of life. He who comes to me will never be hungry. He who believes in me will never thirst. v35