Sahih al-Bukhari 4962

Ismail ibn Abdullah related to us; Malik related to us, from Zayd ibn Aslam, from Abu Salih al-Samman, from Abu Hurayra (may Allah be pleased with him), that the Messenger of Allah (peace and blessings be upon him) said: ‘Horses are of three kinds: for one man they are a reward, for another a protection, and for another a burden of sin. As for the one for whom they are a reward: he is a man who ties them in the path of Allah and lets them graze freely in a pasture or garden. Whatever they eat within that pasture or garden is counted as good deeds for him. If they break their tether and gallop up one or two hills, their hoofprints and dung are good deeds for him. If they pass by a river and drink from it, though he had not intended to water them there, that too is counted as good deeds for him; thus they are a reward for that man. A man who keeps them to enrich himself and avoid asking others for help, while not forgetting Allah’s due upon their necks and backs, has in them a protection. A man who keeps them out of pride, for show, and in opposition to others has in them a burden of sin.’ The Messenger of Allah was asked about donkeys. He said, ‘Nothing has been sent down to me concerning them except this singular, all-encompassing verse: “Whoever does an atom’s weight of good will see it, and whoever does an atom’s weight of evil will see it.”’