(31) باب التَّوَجُّهِ نَحْوَ الْقِبْلَةِ حَيْثُ كَانَ
Narrated Jabir:
Allah's Messenger (ﷺ) 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.
Reference: Sahih al-Bukhari 400
In-book reference: Book 8, Hadith 51
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 1, Book 8, Hadith 393