Sunan an Nasai
492
Sahih+2

It was narrated that Ibn 'Umar said:"The Messenger of Allah (ﷺ) used to pray on his mount while on a journey, no matter what direction it was facing." Malik said: "Abdullah bin Dinar said: 'And Ibn 'Umar used to do likewise

SahihAbu Ghuddah
SahihAl-Albani