Abdullah bin Dinar عبد الله بن دينار العدوي · The Book of Salah

"The Messenger of Allah (ﷺ) used to pray voluntary prayers (Usabbih) while riding his mount, facing whatever direction it was facing, and he would pray Witr likewise, but he would not offer the prescribed prayers on it."

"The Messenger of Allah (ﷺ) used to pray while on his animal when he was coming back from Makkah to Madinah. Concerning this, the verse was revealed: So wherever you turn (yourselves or your faces) there is the Face of Allah.'" Al-Baqarah 2:115.