The Messenger of Allah(ﷺ) forbade the flesh of domestic asses on the day of Khaibar, but permitted horse flesh.
Sunan Abi Dawud Book 28, Hadith 53
← Previous Hadith The Messenger of Allah (ﷺ) forbade riding the camel which feeds on filth and drinking its milk.

Sunan Abi Dawud Book 28, Hadith 52 Next Hadith → On the day of Khaybar we slaughtered horses, mules, and assess. The Messenger of Allah (ﷺ) forbade us (to eat) mules and asses, but he did not forbid horse-flesh.

Sunan Abi Dawud Book 28, Hadith 54