Abu Dawud
General Behavior
Book Number: 036 / Hadith Number: 4860
Narated By Anas ibn Malik : The Prophet (pbuh) said: When I was taken up to heaven I passed by people who had nails of copper and were scratching their faces and their breasts. I said: Who are these people, Gabriel? He replied: They are those who were given to back biting and who aspersed people's honour.