Thus our adversaries teach nothing but the external piety of external good works, which Paul calls the piety of the law; and thus, like the Jews, they see the veiled face of Moses, only strengthening security and hardness of heart in some hypocrites; they lead men upon a sandy foundation, upon their own works, by which means Christ and the Gospel are despised, and give many miserable consciences cause for despair; for they do good works relying upon false conceits, and, never experiencing the great power of faith, they at last sink into despair.
We, however, hold and assert of external piety, that God requires and demands such an external correct life; and that on account of God’s commandment, we must perform the good works prescribed in the Ten Commandments. For the law is our schoolmaster, Gal. 3:24, and is given for the unrighteous. It is the will of the Lord, our God, that gross sins should be restrained by external discipline; and for this purpose, he has given laws, established governments, provided men of learning and wisdom, who are fitted to govern. Human reason can, to some extent, by its own powers, produce an honorable external deportment like this; although it is often hindered in doing so, by innate weakness and the arts of the devil.
Now, although I am willing to allow to this external life and such good works, all the praise that is properly due them;—for in this life and in worldly matters, there is nothing better than honesty and virtue, as Aristotle says: “Neither the morning nor the evening star is more lovely and beautiful than honesty and righteousness,” God himself rewarding such virtues with temporal gifts;—yet, we should not extol good works and such a deportment so as to bring contumely on Christ. The opinion that we must merit the remission of our sins by our works, is certainly a fiction and an error. (Henkel Translation, p. 161-162).