Narrated Jabir bin `Abdullah: The Prophet used to pray (the Nawafil) on his Mount facing east and whenever he wanted to offer the compulsory prayer, he used to dismount and face the Qibla.
Hadith ReferenceSahih Bukhari / The Book of Abridged Or Shortened Prayers (At-Taqsir) / Hadith: 1099
Hadith Gradingمحدثین:أحاديث صحيح البخاريّ كلّها صحيحة