Musnad Ahmad 26:209

Hajjaj narrated to us, Sharik informed us, from al-Rukin ibn al-Rabi', from al-Qasim ibn Hassan, from Abdullah ibn Mas'ud, from the Prophet (peace be upon him), who said: "Horses are of three types: a horse for the Most Merciful, a horse for man, and a horse for the devil. As for the horse of the Most Merciful, it is the one tied in the way of Allah; its fodder, its dung, and its urine—and he mentioned whatever Allah willed. As for the horse of the devil, it is the one used for gambling or betting. As for the horse of man, it is the horse a man ties up, seeking its offspring, so it serves as a covering for him from poverty."