20 “This is the bread that comes down from heaven;” that by eating it we may live, since we cannot have eternal life from ourselves. “Not,” says He, “as your fathers did eat manna, and are dead: he that eats this bread shall live forever.” That those fathers are dead, He would have to be understood as meaning, that they do not live forever. For even they who eat Christ shall certainly die temporally; but they live forever, because Christ is eternal life.
Source: Tractates on the Gospel of John (New Advent)