Musnad Ahmad 30:2498

Yahya narrated to us, from Sufyan, who said: Salam ibn Abd al-Rahman narrated to me, from Abu Zur'ah, from Abu Hurayrah, who said: "The Messenger of Allah, peace and blessings of Allah be upon him, used to dislike the *shikal* (a horse having white markings on one foreleg and the opposite hind leg) among horses."