Sahih Muslim | Book 20 | Hadith Number 4617

Narrated by 'Urwat al-Bariqi
'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.