I saw the Messenger of Allah ﷺ praying on a donkey while heading toward Khaybar.
حدثنا عبد الرحمن عن مالك عن أبي عمرو بن يحيى عن سعيد بن يسار
رأيت رسول الله ﷺ يصلي على حمار وهو موجه إلى خيبر
Its isnad is sahih. It is found in Muwatta 1:165. Muslim also related it, 1:195, as did Abu Dawud, 1:473, both of them through the route of Malik, and Munziri also attributed it to Nasai. In Awn al-Mabud it is reported that Daraqutni and others criticized this hadith, claiming that Amr bin Yahya Mazini erred in saying "on a donkey," and that the correct version is that he prayed on his mount or on the camel! But this whole criticism is arbitrary, for the establishment of one report does not negate the establishment of the other.Amr bin Yahya bin Umara bin Abu Hasan Ansari Mazini is trustworthy. He was deemed trustworthy by Ibn Saad, Abu Hatim, Nasai, and others."Muwajjih," with the jim doubled and vowelled with a kasra, means "facing" or "turning toward." One says, "wajjaha ila kadha," meaning "he turned toward it," as though he directed his face, or his mount, or the like, in that direction. In one manuscript it appears as "al-mutawajjih," which agrees with the version found in Muwatta and Abu Dawud, and these two are what is meant by it. See 4518.