Backbiting and Slandering

Prophet Muhammad (PBUH) said :"Do you know what backbiting is?" They said, "God and His Messenger know best." He then said, "It is to say something about your brother that he would dislike." Someone asked him, "But what if what I say is true?" The Messenger of God said, "If what you say about him is true, you are backbiting him, but if it is not true then you have slandered him." (Muslim)