Musnad Ahmad 31:184

Muhammad ibn Ja'far narrated to us, Shu'bah narrated to us, from Anas ibn Sirin, from Ma'bad, from Abu Sa'id al-Khudri, from the Prophet, may Allah bless him and grant him peace: That he was asked about *al-'azl* (coitus interruptus)? Or he said: Regarding *al-'azl*? He said: "It does not matter if you do not do that, for it is only the decree."