Mukhtasar Bukhari

Narrated from Sayyiduna Anas (may Allah be pleased with him) that he offered prayer while riding a donkey and his face was towards the left of the Qiblah. (When he finished the prayer) he was asked, "You prayed against the direction of the Qiblah?" He replied, "If I had not seen the Messenger of Allah (peace and blessings of Allah be upon him) doing so, I would never have done it."