Luther's Little Instruction Book: The Small Catechism of Martin Luther

IV. Q. How can physical eating and drinking do such great things?

A. Of course, eating and drinking do not do these things. These words, written here, do them: “given for you” and “shed for you to forgive sins.” These words, along with physical eating and drinking are the important part of the sacrament. Anyone who believes these words has what they say and what they record, namely, the forgiveness of sins.