Sahih Bukhari | Volume 1 | Hadith Number 76

Narrated by Ibn 'Abbas
Once I came riding a she-ass and had (just) attained the age of puberty. Allah's Apostle was offering the prayer at Mina. There was no wall in front of him and I passed in front of some of the row while they were offering their prayers. There I let the she-ass loose to graze and entered the row, and nobody objected to it.