Yahya related to me from Malik from Nafi from Abdullah ibn Umarthat the Messenger of Allah, may Allah bless him and grant him peace,held a race between horses which had been made lean by training, fromal-Hafya to Thaniyatu-lWada. He held a race between horses which hadnot been made lean from the Thaniya (a mountain pass near Madina) tothe mosque of the Banu Zurayq. Abdullah ibn Umar was among those whoraced them .
USC-MSA web (English) reference: Book 21, Hadith 45
Arabic reference: Book 21, Hadith 1005