Chapter: [During the obligatory Salat (prayers)] one should face the Qiblah (Kabah at Makkah) wherever one may be
Jabir
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)
Vol. 1, Book 8, Hadith 393
Arabic Text
حَدَّثَنَا مُسْلِمٌ، قَالَ حَدَّثَنَا هِشَامٌ، قَالَ حَدَّثَنَا يَحْيَى بْنُ أَبِي كَثِيرٍ، عَنْ مُحَمَّدِ بْنِ عَبْدِ الرَّحْمَنِ، عَنْ جَابِرٍ، قَالَ كَانَ رَسُولُ اللَّهِ صلى الله عليه وسلم يُصَلِّي عَلَى رَاحِلَتِهِ حَيْثُ تَوَجَّهَتْ، فَإِذَا أَرَادَ الْفَرِيضَةَ نَزَلَ فَاسْتَقْبَلَ الْقِبْلَةَ.