We were afflicted with hunger during the besiege of Khaibar, and when it was the day of (the battle
of) Khaibar, we slaughtered the donkeys and when the pots got boiling (with their meat). Allah's
Apostle made an announcement that all the pots should be upset and that nobody should eat anything
of the meat of the donkeys. We thought that the Prophet (ﷺ) prohibited that because the Khumus had not
been taken out of the booty (i.e. donkeys); other people said, "He prohibited eating them for ever."
The sub-narrator added, "I asked Sa`id bin Jubair who said, 'He has made the eating of donkeys' meat
illegal for ever.")
Sahih al-Bukhari Book 57, Hadith 63