Maliks Muwatta Book 16, Hadith Number 29.
Section : Burying the Dead.
Yahya related to me from Malik that he had heard that Umm Salama, the wife of the Prophet, may Allah bless him and grant him peace, used to say, “I did not believe that the Messenger of Allah, may Allah bless him and grant him peace, had died until I heard the pickaxes fall.”