Musnad Ahmad 32:1745

'Affan narrated to us, Sa'id ibn Zayd narrated to us, he said: Al-Zubayr ibn al-Khirrit narrated to me, from Abu Labid, he said: The horses were sent out during the time of al-Hajjaj, and al-Hakam ibn Ayyub was the governor of Basra. He said: So we came to the horse race, and when the horses arrived, we said: If only we went to Anas ibn Malik and asked him, "Did you use to bet on horse races during the time of the Messenger of Allah, may Allah bless him and grant him peace?" So we came to him while he was in his palace in al-Zawiyah, and we asked him. We said: "O Abu Hamza, did you use to bet on horse races during the time of the Messenger of Allah, may Allah bless him and grant him peace? Did the Messenger of Allah, may Allah bless him and grant him peace, bet on horse races?" He said: "Yes, by Allah. The Messenger of Allah, may Allah bless him and grant him peace, did bet on a horse of his, which was called Subhah. It outpaced the people, so he became elated by that and it pleased him."