Musnad Abu Ya'la al-Mawsili 111:28

Abu Ya'la informed us, Muhammad ibn Jami' al-'Attar narrated to us, Hammad ibn Zayd narrated to us, Ayyub narrated to us, from Nafi', from Abu Hurayrah, who said: The Messenger of Allah (may Allah bless him and grant him peace) said: "Good is tied to the forelocks of horses."