Saeed bin Yasar reported,

I was traveling with Ibn Umar along the road to Mecca. Saeed said, "When I feared that dawn was approaching, I dismounted and prayed witr, then caught up with him."Ibn Umar asked me, "Where were you?"I replied, "I feared the break of dawn, so I dismounted and prayed witr."Abdullah said, "Do you not have in the Messenger of Allah ﷺ an example to follow?"I said, "Yes indeed, by Allah."He said, "The Messenger of Allah ﷺ used to pray witr while riding on his camel."

Muslim 1615

Sahih

و حدثنا يحيى بن يحيى قال قرأت على مالك عن أبي بكر بن عمر بن عبد الرحمن بن عبد الله بن عمر بن الخطاب

عن سعيد بن يسار أنه قال

كنت أسير مع ابن عمر بطريق مكة قال سعيد فلما خشيت الصبح نزلت فأوترت ثم أدركته فقال لي ابن عمر أين كنت فقلت له خشيت الفجر فنزلت فأوترت فقال عبد الله أليس لك في رسول الله ﷺ أسوة فقلت بلى والله قال إن رسول الله ﷺ كان يوتر على البعير

مسلم 1615صحيح
Contents
Reference
Commentary
Ayat
Collection
Sahih Muslim
Book
Travelers' prayer and its shortening
Chapter
Permissibility of praying voluntary prayers on a mount while traveling, whichever direction it faces
Numbering
Darussalam 1615
Muslim 1615