Sahih Muslim Book 1, Hadith Number 186.

Chapter : Beating of the cheeks, tearing of the front opening of the shirt, and calling the calls of the Jihillya (Ignorance) are forbidden.

It is narrated on the authority of Abu Burda b. Abu Musa that Abu Musa was afflicted with grave pain and he became unconscious and his head was in the lap of a lady of his household. One of the women of his household wailed. He (Abu Musa) was unable (because of weakness) to say anything to her. But when he was a bit recovered he said: I have no concern with one with whom the Messenger of Allah (may peace be upon him) has no concern, Verily the Messenger of Allah (may peace be upon him) has no concern with that woman who wails loudly, shaves her hair and tears (her garment in grief).