“Secondly, though you see something bad in your neighbor, you should not despise and condemn him on account of it. Instead you should look at his good qualities and use your own good qualities to help him, by covering up for him, by making him look good, and by giving him your advice, knowing that even if you were the holiest and most pious man on earth, you would become the worst man by judging someone else. God did not give you your gifts for you to tickle yourself with them, but for you to help your neighbor with them when he needs it, and thus by your strength to bear his weakness, by your piety and honor to cover up his sin and to conceal his shame, as God through Christ has done for you and still does every day.  If you refuse to do that, if you insist upon flattering yourself and despising others, you should know that while someone else may have a speck in his eye as far as you are concerned, by comparison you have a log in your eye as far as God is concerned (Matt. 7:3). (Luther’s Works, v. 21, pages 218-219).

You do not imagine, do you, that God is unable to spread out an account book before your very nose and to cite not only your transgressions and the sins of your youth (Ps. 25:7), but also your whole life, which you thought was very precious, as the monks think about their cloister life? How will you stand before Him then and answer for blaspheming and crucifying His Son daily with your Masses and other idolatry? This is what happens when we forget what we used to be like. Then it is easy to judge other people. But the command is: “Hans, take hold of your own nose, and reach into your own bosom. If you are looking for a villain on whom to pass judgment, you will find there the biggest villain on earth. You will just as soon forget about other people and gladly let them alone. You will never find as much sin in another person as you will in yourself. If you see a great deal of another person, you see one year or two. But when you look at yourself, you see your whole life, especially the serious blemishes that nobody else knows about. And then you must be ashamed of yourself.   That, you see, would be a good cure for this shameful vice. You would stop pleasing yourself and pray God to forgive you and others.” (Luther’s Works, v. 21, pages 218).

You must understand this in such a way that it does not take away the right of the man in the public ministry of preaching to judge matters of doctrine as well as of life. Indeed, it is incumbent on him in his office to rebuke publicly whatever does not square with true doctrine, for the very purpose of preventing sects from coming in and taking hold. When he sees that life is wrong, he must likewise denounce it and resist it. He is put there to oversee this, and he will have to give account of it (Heb. 13:17). In fact, whenever any Christian sees his neighbor doing wrong, he has the duty of admonishing him and restraining him, which is impossible without judging and passing judgment. But this is all done on the basis of an office or a commission, which Christ, is not discussing here, as we have said often enough. What is forbidden is that everyone may go ahead on the basis of his own ideas and make a doctrine and spirit of his own, imagining that he is to be Master Smart Aleck, who is supposed to correct everybody and to criticize him, though he has no commission to do anything of the sort. These are the people that the Lord is denouncing here. He does not want anyone to undertake or to do anything on the basis of his own ideas and without a commission, especially not the task of judging other people.

(Luther’s Works, v. 21, pages 212-213).