Fighting for the Cause of Allah (Jihaad)
Bukhari :: Book 4 :: Volume 52 :: Hadith 121
Narrated Abdullah:
The Prophet arranged for a horse race of the horses which had not been made lean; the area of the race was from Ath-Thaniya to the mosque of Bani Zuraiq. (The sub-narrator said, "'Abdullah bin 'Umar was amongst those who participated in that horse race.").