Whoever does not want to trust in God’s word and to take his stand on these or on similar passages, ‘What God says, he can do’ [Rom. 4:21], and ‘God cannot lie’ [Hebrews 6:18], I faithfully counsel him to leave Holy Scripture and the articles of the Christian faith alone. For his interpretation constantly drags him deeper into error. It would be better for him to remain a condemned heathen than that he should become a condemned Christian.
O dear man! If someone does not want to believe the article of faith concerning the Lord’s Supper, how will he ever believe the article of faith concerning the humanity and divinity of Christ in one person? If you have doubts about whether you are receiving the body of Christ orally when you eat the bread from the altar, likewise, that you are receiving the blood of Christ orally when you drink the wine in the Lord’s Supper, then you must surely have serious doubts (especially when the end of your life draws near) about how the infinite and incomprehensible Godhead, who is and must essentially be everywhere, can be bodily enclosed and included in the humanity and in the Virgin’s body, as St. Paul says in Colossians [2:9]: ‘In him the whole fulness of deity dwells bodily.’ …
The devil cannot be idle. Wherever he instigates one heresy, there he must instigate additional ones, and no error remains alone. If the ring is broken at one point, it is no longer a perfect ring; it no longer holds together and constantly comes apart. [Martin Luther, “Brief Confession Concerning the Holy Sacrament,” LW 38:306-307]