So they said to him, "What sign can you do, that we may see and believe in you? What can you do? Our ancestors ate manna in the desert, as it is written: 'He gave them bread from heaven to eat.'" So Jesus said to them, "Amen, amen, I say to you, it was not Moses who gave the bread from heaven; my Father gives you the true bread from heaven. For the bread of God is that which comes down from heaven and gives life to the world." So they said to him, "Sir, give us this bread always." Jesus said to them, "I am the bread of life; whoever comes to me will never hunger, and whoever believes in me will never thirst. (Jn 6:30-35)
People cannot get bread from heaven on demand. Even what the ancestors ate in the desert was not the work of Moses. It is from heaven and if it is God sent then it cannot happen as we expect. God sent has a new standard to which one should adhere to.
It is the recognition that in Jesus and everything that he is doing, the same God is at work who was at work in the exodus. People have seen Jesus doing a sign (feeding the people) and it is really strange that they ask for another. Unless they asked him for a political or military type of intervention to which Jesus was not willing to.
There was only one answer to all their questions and the answer was standing in front of them and that was Jesus. This passage has one of the ‘I am’ sayings in John’s gospel. In fact this is the first one of such sayings. Unless they recognize who Jesus is, they may be fed with bread and fish, but the deep hunger within the will never be satisfied. Jesus is the answer to all questions.