Sahih Muslim Book 20, Hadith Number 4617.

Chapter : Great benefit in the forelocks of the horses.

‘Urwat al-Bariqi reported Allah’s Messenger (may peace be upon him) having said this: Good is tied to the forelock of the horses. It Was said to him: Messenger of Allah, why is it so? He (the Holy Prophet said): For reward and booty until the Day of Judgment.