they went on a military campaign with the Messenger of Allah to Khaibar, and the people were starving. They found some domesticated donkeys there, so the people slaughtered some of them. The Prophet was told about that, and he ordered 'Abdur-rahman bin 'Awf to announce to the people: "The flesh of domesticated donkeys is not permissible for the one who testifies that I am the Messenger of Allah." (Using translation from Nasāʾī 4341)
أَنَّهُ حَدَّثَهُمْ أَنَّهُمْ غَزَوْا مَعَ رَسُولِ اللهِ ﷺ إِلَى خَيْبَرَ وَالنَّاسُ جِيَاعٌ فَوَجَدُوا فِيهِ حُمُرًا مِنْ حُمُرِ الْإِنْسِ فَذَبَحَ النَّاسُ مِنْهَا فَحُدِّثَ بِذَلِكَ رَسُولُ اللهِ ﷺ فَأَمَرَ عَبْدَ الرَّحْمَنِ بْنَ عَوْفٍ فَأَذَّنَ فِي النَّاسِ «أَلَا إِنَّ لُحُومَ الْحُمُرِ الْإِنْسِ لَا تَحِلُّ لِمَنْ شَهِدَ أَنِّي رَسُولُ اللهِ ﷺ»