"On the Day of Khaibar, the Messenger of Allah forbade the flesh of domesticated donkeys, cooked or raw."
Sunan an-Nasa'i Book 42, Hadith 76
← Previous Hadith A similar report was narrated from Ibn 'Umar, but he did not mention Khaibar,

Sunan an-Nasa'i Book 42, Hadith 75 Next Hadith → "On the Day of khaiber we caught some donkeys outside the village and we cooked them. Then the caller of the Prophet called out: 'The Messenger of Allah has forbidden the flesh of donkeys, so turn over your cooking pots with whatever is in them.' So we turned them over."

Sunan an-Nasa'i Book 42, Hadith 77