The Book of Prayers (Kitab Al-Salat)
Muslim :: Book 4 : Hadith 1020
Abdullah b. Abbas reported that he came riding on a donkey, and the Messenger of Allah (may peace be upon him) was leading the people in prayer at Mina on the occasion of the Farewell Pilgrimage and (the narrator) reported: The donkey passed in front of the row and then he got down from it And joined the row along with the people.