Musnad Ahmad 27:147

Sufyan narrated to us, Ismail bin Umayyah narrated to us, from Nafi’, from Ibn Umar, who said: "The Messenger of Allah (ﷺ) held a horse race. He sent those that were trained (for racing) from Al-Hafya’, and he sent those that were not trained from Thaniyat al-Wada’ to the mosque of Banu Zurayq."