سنن النسائي

It was narrated that Abu Hurairah said: "The Messenger of Allah (ﷺ) said: 'There is goodness tied to the forelocks of horses until the Day of Resurrection. And horses are of three types: Those that bring reward to man, those that are a means of protection for a man, and those that are a burden (of sin) for a man. As for those that bring reward, they are kept for the cause of Allah and for Jihad. No fodder enters their stomach but for everything that enters their stomachs, reward is written for him, even if he puts them out to pasture.'" And he quoted the Hadith.