Guarding Against the Tongue – The Six Exceptions to Backbiting and how to Prevent it!
A man once said to Al-Hasan Al-Basree: “You have backbitten me.” Al Hasan al Basree replied: “Who are you, so that I may know to whom my good deeds are going?”
Lecture goes into great detail about the Six Instances in which one is excused of the sin of backbiting. Also how to prevent oneself from backbiting