Musnad Ahmad 1060:22

'Affan narrated to us, Hammam narrated to us, Ishaq, the nephew of Anas, informed us, from Rafi' ibn Ishaq, from Abu Ayyub, that he said: We do not know what to do with the latrines of Egypt, for the Messenger of Allah (peace and blessings of Allah be upon him) has forbidden us from facing the two qiblas or turning our backs to them. And Hammam said: "Meaning for defecation and urination."