Sahih Bukhari, Chapter: Jihaad (Fighting for the cause of Allah)

Musa bin Uqba said, Nafi said: Ibn Umar said, "Allah's Apostle (SAW) arranged a horse race amongst the horses that had been made lean, letting them start from Al-Hafya and their limit (distance of running) was up to Thaniyat-al-Wada. I asked Musa, 'What was the distance between the two places?' Musa replied, 'Six or seven miles. He arranged a race of the horses which had not been made lean sending them from Thaniyat-al-Wada, and their limit was up to the mosque of Bani Zuraiq.' I asked, 'What was the distance between those two places?' He replied 'One mile or so.' Ibn Umar was amongst those who participated in that horse race."