Al Ayyashi...
Al Ayyashi, from Hareyz who said, ‘Abu Ja’far -asws said: ‘Allah -azwj Revealed this Verse regarding the optional Salat in particular: therefore wherever you turn to, so there would be the Face of Allah; surely Allah is Capacious, Knowing [2:115] , and Rasool-Allah -saww prayed Salat in gestures being upon his ‑saww riding animal wherever it headed with him -saww when he -saww went out to (Battle of) Khyber, and when he -saww returned from Makkah, and he -saww made the Kabah to be behind his -saww back’’.
Muhammad Bin Yahya, from Ahmad Bin Muhammad, from Muhammad Bin Sinan, from Ibn Muskan, (It has been narrated) from Al-Halby who asked Abu Abdullah -asws about the optional Salāt upon the camel and the riding animal. So he -asws said: ‘Yes, whichever direction you may be facing’. So I said, ‘Upon the camel and the riding animal?’ He -asws said ‘Yes, whichever direction you may be’.
Ali Bin Ibrahim, from his father, from Ibn Abu Umery, from Abdul Rahman Bin Al Hajjaj, (It has been narrated) from Abu Abdullah -asws regarding the man who prays the optional Salāt in the cities, and he is upon a riding animal, wherever he may be facing with it’. So he -asws said: ‘Yes, there is no problem’.