Anas ibn Malik · The Book of Horses, Races and Shooting

"Horses may bring reward to a man, or they may be a means of protection, or they may be a burden (of sin). As for that which brings reward, it is a man who keeps it for the cause of Allah and ties it with a long rope in a pasture or a garden; whatever it eats or drinks in that pasture or garden will count as good deeds for him. If it breaks its rope and jumps over one…

"A mule was given as a gift to the Messenger of Allah and he rode it." 'Ali said: "If we mate a donkey with a horse, we will have one like this." The Messenger of Allah said: "That is only done by those who do not know."

It was narrated from Ibn 'Umar that the Messenger of Allah organized a race for horses that had been made lean, from Al-Hafya' and its finish line was Thaniyyat Al-Wada', and he organized another race for horses that had not been made lean, from Ath-Thaniyyah to the Masjid of Banu Zuraiq, and 'Abdullah was among those who took part in the race.