Musannaf Ibn Abi Shayba 28:44

Al-Fadl ibn Dukayn narrated to us, he said: Musa ibn Ali narrated to us, he said: I heard my father narrating that a man came to the Messenger of Allah, may Allah bless him and grant him peace, and said: "I want to tether a horse or buy a horse." He said: So he said: "You should get one that is *aqrah* (having a white blaze on the forehead), *artham* (having a white mark on the upper lip), *kumayt* (bay-colored), or *adham* (black-colored) that is *muhajjal* (having white markings on the legs) and *taliq al-yumna* (having no white marking on the right leg)."