(5) باب تَحْرِيمِ أَكْلِ لَحْمِ الْحُمُرِ الإِنْسِيَّةِ
Ibn 'Abbas reported:
I do not know whether Allah's Messenger (ﷺ) prohibited (the eating of the domestic ass) due to the fact that they were the beasts of burden for the people, so he (the Holy Prophet) did not like their beasts of burden to be destroyed (as a matter of expediency), or he prohibited the use of the flesh of domestic asses (not as an expediency but as a law of the Shari'ah) on the Day of Khaibar.
Reference: Sahih Muslim 1939
In-book reference: Book 34, Hadith 46
USC-MSA web (English) reference(deprecated numbering scheme): Book 21, Hadith 4774