After Jesus declared to the crowd, "I AM the Bread of Life," He had to convince them that the "bread of heaven" was not Manna, but Him. He had to show them that Manna was temporary, but He is eternal. He had to inform them that those who ate Manna still died, but those who believe in Him will never die. Manna was sent by God to give life to His people physically for "now," but Jesus was sent by God to give life spiritually, for now and forever.