Narrated Ibn Abi Aufa:

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 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 Said bin Jubair who said, 'He has made the eating of donkeys' meat illegal for ever.")

حَدَّثَنَا مُوسَى بْنُ إِسْمَاعِيلَ، حَدَّثَنَا عَبْدُ الْوَاحِدِ، حَدَّثَنَا الشَّيْبَانِيُّ، قَالَ سَمِعْتُ ابْنَ أَبِي أَوْفَى ـ رضى الله عنهما ـ يَقُولُ أَصَابَتْنَا مَجَاعَةٌ لَيَالِيَ خَيْبَرَ، فَلَمَّا كَانَ يَوْمُ خَيْبَرَ وَقَعْنَا فِي الْحُمُرِ الأَهْلِيَّةِ، فَانْتَحَرْنَاهَا فَلَمَّا غَلَتِ الْقُدُورُ، نَادَى مُنَادِي رَسُولِ اللَّهِ ﷺ اكْفَئُوا الْقُدُورَ، فَلاَ تَطْعَمُوا مِنْ لُحُومِ الْحُمُرِ شَيْئًا. قَالَ عَبْدُ اللَّهِ فَقُلْنَا إِنَّمَا نَهَى النَّبِيُّ ﷺ لأَنَّهَا لَمْ تُخَمَّسْ. قَالَ وَقَالَ آخَرُونَ حَرَّمَهَا الْبَتَّةَ. وَسَأَلْتُ سَعِيدَ بْنَ جُبَيْرٍ فَقَالَ حَرَّمَهَا الْبَتَّةَ.