Musannaf Ibn Abi Shayba 1:1610

Affan narrated to us, he said: Wuhayb narrated to us, he said: Amr ibn Yahya narrated to us, from Abu Zayd, from Ma'qil ibn Abi Ma'qil, from the Prophet (may Allah bless him and grant him peace), that he forbade us from facing either of the two qiblas while defecating or urinating.