حَدَّثَنَا عَبْدُ اللَّهِ بْنُ مُحَمَّدٍ، حَدَّثَنَا أَبُو عَامِرٍ، حَدَّثَنَا إِسْرَائِيلُ، عَنْ مَجْزَأَةَ بْنِ زَاهِرٍ الأَسْلَمِيِّ، عَنْ أَبِيهِ ـ وَكَانَ مِمَّنْ شَهِدَ الشَّجَرَةَ ـ قَالَ إِنِّي لأُوقِدُ تَحْتَ الْقِدْرِ بِلُحُومِ الْحُمُرِ إِذْ نَادَى مُنَادِي رَسُولِ اللَّهِ صلى الله عليه وسلم إِنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم يَنْهَاكُمْ عَنْ لُحُومِ الْحُمُرِ‏.‏

Narrated Zahir Al-Aslami: (who was one of those who had witnessed (the Pledge of allegiance beneath) the Tree) While I was making fire beneath the cooking pots containing donkey's meat, the announcer of Allah's Messenger (PBUH) announced, "Allah's Messenger (PBUH) forbids you to eat donkey's meat." Translation Not Available

Book Ref: Sahih Bukhari Book 64 Hadith 4173
Web Ref:  Sahih Bukhari Vol 5 Book 59 Hadith 491