Ambrose of Milan

All those who ate that bread [manna] died in the desert, but this food which you receive, this "living bread which came down from heaven," furnishes the energy for eternal life. Whoever eats this bread "will not die forever," for it is the body of Christ. … That manna was subject to corruption if kept for a second day. This is foreign to every corruption. Whoever tastes it in a holy manner shall not be able to feel corruption. For them water flowed from the rock. For you blood flows from Christ. Water satisfied them for the hour. Blood satisfies you for eternity.