Narrated Ursa bin ALGA: The Prophet said, "Good will remain (as a permanent quality) in the foreheads of horses till the Day of Resurrection." And narrated Anas bin Malik: Allah's Apostle said, "There is a blessing in the fore-heads of horses."
— Sahih Bukhari, Volume 4, Book 52: Fighting for the Cause of Allah (Jihaad), Hadith #103