Sahih Bukari, Volume 4, Book 56, Number 839:
Quote:
Narrated Abu Huraira:
As for the one for whom it is a source of reward, he is the one who keeps his horse for the sake of Jihad in Allah's Cause; he ties it with a long rope on a pasture or in a garden. So whatever its rope allows it to eat, will be regarded as good rewardable deeds (for its owner). And if it breaks off its rope and jumps over one or two hillocks, even its dung will be considered amongst his good deeds.