(a) It is narrated from Anas bin Sirin that when Anas bin Malik (may Allah be pleased with him) came from Sham, we went to meet him. I met him at a place called "Ayn al-Tamr". He (may Allah be pleased with him) was offering prayer seated on a donkey, and his face was to the left of the qiblah. I said to him: I see you praying facing other than the qiblah! He said: "Had I not seen the Messenger of Allah (peace and blessings be upon him) doing so, I would never have done so."
(b) And in the hadith of Affan it is that his face was towards that side, and Hammam indicated by gesture: to the left of the qiblah. At the end of this narration it is: "Then I too would not have done so."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2207