Musnad Ahmad 1248:8

'Abd al-Razzaq narrated to us, he said: Ibn Jurayj informed us, he said: 'Amr ibn Yahya al-Ansari informed me, from Abu Zayd, the freed slave of Tha'labah, who informed him, from Ma'qil ibn Abi Ma'qil al-Ansari—one of the companions of the Prophet, may Allah bless him and grant him peace—that he narrated to him: "That the Prophet, may Allah bless him and grant him peace, forbade facing the two qiblahs for defecation and urination."