Musnad Ahmad 773:15

Muhammad ibn Ja‘far narrated to us, Shu‘bah narrated to us, from Husayn, from al-Sha‘bi, who said: I heard ‘Urwah ibn al-Ja‘d al-Bariqi say: I heard the Prophet, peace and blessings of Allah be upon him, say: "Good is tied to the forelocks of horses until the Day of Resurrection: reward and spoils of war."