Abu Huraira reported Allah’s Messenger (may peace be upon him) as saying:
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?
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.
………..and Allah the Almighty says in the Quran:
O you who believe! Avoid much suspicion; indeed some suspicions are sins. And spy not, neither backbite one another. Would one of you like to eat the flesh of his dead brother? You would hate it (so hate backbiting) . And fear Allah. Verily, Allah is the One Who forgives and accepts repentance, Most Merciful.
( سورة الحجرات , Al-Hujraat, Chapter #49, Verse #12)