"The Messenger of Allah forbade Mut'ah and the flesh of domesticated donkeys on the Day of Khaibar." (Using translation from Nasāʾī 4335)  

لِابْنِ عَبَّاسٍ «نَهَى رَسُولُ اللَّهِ ﷺ عَنْ مُتْعَةِ النِّسَاءِ يَوْمَ خَيْبَرَ وَعَنْ لُحُومِ الْحُمُرِ الْإِنْسِيَّةِ»  

[Machine] "O Messenger of Allah, the donkeys have been eaten or are being slaughtered." Then he said, "O Messenger of Allah, the donkeys have been slaughtered or are being eaten." So the Messenger of Allah ﷺ ordered a man to announce, "Indeed, Allah and His Messenger prohibit you from consuming donkey meat, as it is impure."  

يَا رَسُولَ اللَّهِ أُكِلَتِ الْحُمُرُ أَوْ أُفْنِيَتِ الْحُمُرُ ثُمَّ قَالَ يَا رَسُولَ اللَّهِ أُفْنِيَتِ الْحُمُرُ أَوْ أُكِلَتِ الْحُمُرُ فَأَمَرَ رَسُولُ اللَّهِ ﷺ رَجُلًا فَنَادَى «إِنَّ اللَّهَ وَرَسُولَهُ يَنْهَيَانِكُمْ عَنْ لُحُومِ الْحُمُرِ فَإِنَّهَا رِجْسٌ»