1. "Do you know what is backbiting?"
They (the Companions) said: "Allah and His Messenger know best."Thereupon he (the Holy Prophet) said: Backbiting implies your talking about your brother in a manner which he does not like. It was said to him: "What is your opinion about this that if I actually find (that failing) in my brother which I made a mention of?" He said: "If (that failing) is actually found (in him) what you assert, you in fact backbited him, and if that is not in him it is a slander."
[Sahih Muslim 2589]