Musannaf Ibn Abi Shayba 13:857

Abu Bakr narrated to us, he said: Abu al-Ahwas narrated to us, from Simak ibn Harb, from Ikrimah, from Ibn Abbas, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Do not face the Qiblah, and do not turn your backs to it."