The Prophet ﷺ used to visit me when I was sick, not riding a mule nor a mount of mixed breed.
حدثنا أحمد بن حنبل حدثنا عبد الرحمن بن مهدي عن سفيان عن محمد بن المنكدر
كان النبي ﷺ يعودني ليس براكب بغل ولا برذون
Bukhari narrated it in the Book of the Sick, chapter "Visiting the Sick While Riding, Walking, or Riding Behind Someone on a Donkey," no. 5664, from the hadith of Abdul-Rahman bin Mahdi, with the same chain, and it is also in Musnad Ahmad, 3/373.