It is narrated from Sayyiduna Anas (may Allah be pleased with him) that when the Messenger of Allah (peace and blessings be upon him) intended to offer a voluntary prayer on his mount, he would first face the Qiblah and say Allahu Akbar for the prayer, then he would let his mount go wherever it wished, and he (peace and blessings be upon him) would continue his prayer, regardless of which direction the mount turned.