Mukhtasar Muslim

Narrated from Sayyiduna Abu Hurairah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings of Allah be upon him) said: Do you know what backbiting is? The people said: Allah and His Messenger know best. He (peace be upon him) said: Backbiting is that you mention about your brother something which he would dislike (if he were present). The people said: O Messenger of Allah! What if that fault is actually present in our brother? He (peace be upon him) said: If that fault is in him, then you have backbitten him; and if it is not in him, then it is slander and false accusation.