Jesus said to them, “I am the bread of life; whoever comes to me shall not hunger, and whoever believes in me shall never thirst. (John 6:35)
Commenting on this verse, Martin Luther said:
He says of Himself that He is a bread, food, and nourishment which not only preserves life and refreshes the body, but a bread – this He states later (v. 58) – which gives eternal life to him who eats it. This bread is to be a preservative against death. It is as if a physician or a pharmacist were to tell a patient: “I will give you a medicine, a potion or purgative, that will save you from death. You will no longer live in fear of death, since you are immune.” Luther’s Works, v. 23, 41
He says: “Hold to Me! Come to Me, and you shall live!” But is it not true that I do die? Just listen to His answer to this question (John 11:25): “Though he die, yet shall he live.” Luther’s Works, v. 23, 44
The words “to eat” stand out prominently here; they mean “to believe.” For it is faith alone that He calls spiritual food. Whoever believes in Christ eats this bread. If anything else were needed to still his hunger and to quench this thirst, Christ would tell us. But He says: “Whoever believes in this Man has this spiritual food and drink.” Luther’s Works, v. 23, 49