Those who do not commit sins and have been gifted with safety (from sins) should take pity on sinners and other disobedient people. Gratefulness should be mostly their indulgence and it should prevent them from (finding faults with) others. What about the backbiter who blames his brother and finds fault with him? Does he not remember that Allah has concealed the sins which he committed while they were bigger than his brother's sins pointed out by him? How can he vilify him about his sins when he has himself committed one like it? Even if he has not committed a similar sin he must have committed bigger ones. By Allah, even if he did not commit big sins but committed only small sins, his exposing the sins of people is itself a big sin.
O creature of Allah, do not be quick in exposition anyone's sin for he may be forgiven for it, and do not feel yourself safe even for a small sin because you may be punished for it. Therefore, every one of you who comes to know the faults of others should not expose them in view of what he knows about his own faults, and he should remain busy in thanks that he has been saved from what others have been indulging in.
(1) Al-'Amidi, Ghurar, 135, 359.