Jabir b. 'Abdullah reported that Allah's Messenger (ﷺ) prohibited eating of the flesh of domestic asses on the Day of Khaibar, and permitted the cooking of the flesh of horses.
Sahih Muslim Book 34, Hadith 51
← Previous Hadith When it was the Day of Khaibar a visitor came and said: Messenger of Allah, the asses have been eaten. Then another came and said: Messenger of Allah, the asses are being destroyed. Then Allah's Messenger (ﷺ) commanded Abu Talha to make an announcement that Allah and His Messenger have prohibited you (from eating) of the flesh of (domestic) asses, for these are loathsome or impure. He (the narrator) said: The earthein pots were turned over along with what was in them.

Sahih Muslim Book 34, Hadith 50 Next Hadith → We ate during the time of Khaibar the (flesh) of horses and of wild asses, but Allah's Messenger (ﷺ) prohibited us (to eat) the flesh of domestic asses.

Sahih Muslim Book 34, Hadith 52