When Jesus fed the five thousand with five loaves they began saying “This must be the prophet.” They were referring to what we find in Chapter Eighteen of Deuteronomy when Moses was warning them against listening to soothsayers. He told them in that verse 15, “A prophet like me will the Lord your God raise up for you from among your kinsmen. Listen to him.”
They embellished that prophecy by adding to it the prediction that when that prophet came, he would also make manna fall from heaven. That is what they had in mind in asking Jesus, “What sign can you do?”
Jesus told them that Moses did not give true heavenly bread. People say that aphids feeding on desert shrubs drop a honey-like substance that the Bedouins refer to as “manna.” Maybe Jesus was saying that was what Moses gave them.