We, however, will build not at all on man’s work but strictly on God’s, which is not only certain and neither fails nor deceives but also, once done, lasts and avails forever. It never needs to be changed or renewed the way men’s deeds and ways change and shift. Take, for instance, the patriarchs in the Old Testament, who also had a baptism, which was the Ten Commandments. As St. Paul says, “They were baptized with the cloud into Moses” (1 Corinthians 10:2), that is, in the Ten Commandments, on the basis of which God made a covenant with them through Moses. Yet there were many thousands among them who did not believe but practiced idolatry, blasphemed God, and rebelled, etc. Should they have said therefore that the Ten Commandments were obsolete, and God could make some different ones? Or when David had his terrible fall into both adultery and murder, should he have said therefore that the Fifth and Sixth Commandments were void and God had to give him others? Then He would have to make another Ten Commandments for the world every single moment.
But the fact is: God’s Commandments are and remain eternally. Even if we fall away from them and do not keep them, and all the world goes to the devil, they will not fall away, but the requirement and duty to keep them remains regardless, no matter how often and how low we fall.
From a sermon on Baptism by Martin Luther, delivered in 1534
Benjamin T.G. Mayes (editor) Martin Luther on Holy Baptism: Sermons to the People (1525-39) 54