The Messenger of Allah ﷺ used to pray on his mount in whatever direction it faced.
حدثنا قران بن تمام عن عبيد الله عن نافع
أن رسول الله ﷺ كان يصلي على راحلته حيث توجهت به
Its isnad is sahih. Qaran bin Tammam Asadi Walibi is trustworthy, one of the teachers of Ahmad. He was deemed trustworthy by Ahmad himself, Ibn Main, Daraqutni, and others. Ibn Main said, "He used to sell livestock, a truthful and trustworthy man." Ahmad said, "I heard from him in the year 181." Bukhari mentioned him in al-Kabir, 1/4/203.Qaran is spelled with a dammah on the qaf, a doubled ra, and ending in a nun.This hadith is similar in meaning to number 4770, and it is an abridgment of number 4714.