Sunan an-Nasa'i, Volume 5, Book 42, Hadith 4348 (DarusSalam) ⓘ
It was narrated that Jabir said: "On the Day of Khaibar we ate the flesh of horses, and onagers, but the Prophet forbade us (from eating) donkeys."(sahih)
أَخْبَرَنَا قُتَيْبَةُ، قَالَ حَدَّثَنَا الْمُفَضَّلُ، - هُوَ ابْنُ فَضَالَةَ - عَنِ ابْنِ جُرَيْجٍ، عَنْ أَبِي الزُّبَيْرِ، عَنْ جَابِرٍ، قَالَ أَكَلْنَا يَوْمَ خَيْبَرَ لُحُومَ الْخَيْلِ وَالْوَحْشِ وَنَهَانَا النَّبِيُّ صلى الله عليه وسلم عَنِ الْحِمَارِ .
also referenced under: Hadith 4343 (Reference) & Book 42, Hadith 81 (In-Book)