Sunan Abi Dawud Book 28, Hadith 53

The Messenger of Allah(ﷺ) forbade the flesh of domestic asses on the day of Khaibar, but permitted horse flesh.

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The Messenger of Allah (ﷺ) forbade riding the camel which feeds on filth and drinking its milk.

Sunan Abi Dawud Book 28, Hadith 52
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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