Sahih Bukhari Volume 5, Book 59, Hadith Number 696.

Narrated By ‘Abdullah bin ‘Abbas : That he came riding a donkey when Allah ‘s Apostle was standing at Mina during Hajjat-ul-Wada’, leading the people in prayer. The donkey passed in front of a part of the row (of the people offering the prayer). Then he dismounted from it and took his position in the row with the people.