Sahih Bukhari
Sahih Bukhari Volume 001, Book 008, Hadith Number 393.
Hadith Section/Book: Sahih Bukhari Sahih Bukhari Book 08. Prayers (Salat)
Narated By Jabir : Allah's Apostle used to pray (optional, non-obligatory prayer) while riding on his mount (Rahila) wherever it turned, and whenever he wanted to pray the compulsory prayer he dismounted and prayed facing the Qibla.