There are very many who, when they hear of this freedom of faith, immediately turn it into an occasion for the flesh and think that now all things are allowed them. They want to show that they are free men and Christians only by despising and finding fault with ceremonies, traditions, and human laws; as if they were Christians because on stated days they do not fast or eat meat when others fast, or because they do not use the accustomed prayers, and with upturned nose scoff at the precepts of men, although they utterly disregard all else that pertains to the Christian religion. The extreme opposite of these are those who rely for their salvation solely on the reverent observance of ceremonies, as if they would be saved because on certain days they fast or abstain from meats, or pray certain prayers; these make a boast of the precepts of the church and of the fathers, and do not care a fig for the things which are of the essence of our faith. Plainly, both are in error because they neglect the weightier things which are necessary to salvation, and quarrel so noisily about trifling and unnecessary matters.
-- Martin Luther, The Freedom of a Christian in John Dillenburger, ed., Martin Luther: Selections from His Writings