Malik related to me from al-Walid ibn Abdullah ibn Sayyad thatal-Muttalib ibn Abdullah ibn Hantab al-Makhzumi informed him that aman asked the Messenger of Allah, may Allah bless him and grant himpeace, "What is backbiting?" The Messenger of Allah, may Allah blesshim and grant him peace, said, "It is to mention about a man what hedoes not want to hear." He said, "Messenger of Allah! Even if it istrue?" The Messenger of Allah, may Allah bless him and grant himpeace, said, "If you utter something false, then it is slander."
USC-MSA web (English) reference: Book 56, Hadith 10
Arabic reference: Book 56, Hadith 1823