Virtues of the Prayer Hall (Sutra of the Musalla)

Bukhari :: Book 1 :: Volume 9 :: Hadith 472

Narrated Ibn 'Abbas:

Once I came riding a she-ass when I had just attained the age of puberty. Allah's Apostle was offering the prayer at Mina with no wall in front of him and I passed in front of some of the row. There I dismounted and let my she-ass loose to graze and entered the row and nobody objected to me about it.