Musnad Abu Ya'la al-Mawsili 153:51

Mus'ab ibn 'Abd Allah al-Zubayri narrated to us, 'Abd al-'Aziz ibn Muhammad narrated to us, from 'Ubayd Allah, from Nafi' and Salim, from Ibn 'Umar: That the Messenger of Allah (may Allah bless him and grant him peace) forbade the eating of the meat of domesticated donkeys.