I saw the Messenger of Allah ﷺ praying on a donkey while heading toward Khaybar.
أخبرنا قتيبة بن سعيد عن مالك عن عمرو بن يحيى عن سعيد بن يسار
رأيت رسول الله ﷺ يصلي على حمار وهو متوجه إلى خيبر
Reported by Muslim, Prayer of the Traveler, chapter on the permissibility of performing voluntary prayer while riding a mount during travel in whatever direction it faces, hadith no. 35/700, from the hadith of Malik through this same chain. It is also found in the Muwatta (Yahya's version), 1/150-151, and in Kubra, hadith no. 819.