Silsilat al-Ahadith al-Sahihah

It is narrated Mursal from Sayyiduna Mutalib bin Abdul Malik bin Hantab that a man asked the Messenger of Allah (peace and blessings be upon him): "What is backbiting?" The Messenger of Allah (peace and blessings be upon him) said: "To mention something about a person which he dislikes to hear." He said: "O Messenger of Allah! Even if that thing is true (and correct)?" The Messenger of Allah (peace and blessings be upon him) said: "If you have said something untrue (about someone), then that is slander (not backbiting)."