كتاب الصيد والذبائح وما يؤكل من الحيوان
34  
The Book of Hunting, Slaughter, and what may be Eaten
(5)
Chapter: The prohibition of eating the meat of domesticated donkeys
(5)
باب تَحْرِيمِ أَكْلِ لَحْمِ الْحُمُرِ الإِنْسِيَّةِ ‏‏
Sahih Muslim 1940 a

Anas reported:

When Allah's Messenger (ﷺ) conquered Khaibar, we caught hold of the asses outside the village. We cooked them (their flesh). Then the announcer of Allah's Messenger (ﷺ) made the announcement: Listen, verily Allah and His Messenger have prohibited you (the eating of) their (flesh), for it is a loathsome evil of Satan's doing. Then the earthen pots were turned over along with what was in them, and these were brimming (with flesh) at that time.
وَحَدَّثَنَا ابْنُ أَبِي عُمَرَ، حَدَّثَنَا سُفْيَانُ، عَنْ أَيُّوبَ، عَنْ مُحَمَّدٍ، عَنْ أَنَسٍ، قَالَ لَمَّا فَتَحَ رَسُولُ اللَّهِ صلى الله عليه وسلم خَيْبَرَ أَصَبْنَا حُمُرًا خَارِجًا مِنَ الْقَرْيَةِ فَطَبَخْنَا مِنْهَا فَنَادَى مُنَادِي رَسُولِ اللَّهِ صلى الله عليه وسلم أَلاَ إِنَّ اللَّهَ وَرَسُولَهُ يَنْهَيَانِكُمْ عَنْهَا فَإِنَّهَا رِجْسٌ مِنْ عَمَلِ الشَّيْطَانِ ‏.‏ فَأُكْفِئَتِ الْقُدُورُ بِمَا فِيهَا وَإِنَّهَا لَتَفُورُ بِمَا فِيهَا ‏.‏
Reference : Sahih Muslim 1940a
In-book reference : Book 34, Hadith 49
USC-MSA web (English) reference : Book 21, Hadith 4777
  (deprecated numbering scheme)