Musannaf Ibn Abi Shayba 16:90

Abu Bakr narrated to us, he said: Ibn ‘Ulayyah narrated to us, from Hisham al-Dastawa’i, from Yahya ibn Abi Kathir, from the freed slave of Nafi’ ibn ‘Alqamah, that Ibn ‘Abbas used to dislike the meat of horses, mules, and donkeys. And he used to say: Allah, the Majestic is His praise, said: "And the grazing livestock He has created for you; in them is warmth and [numerous] benefits, and from them you eat." So these are for eating. "And the horses, mules and donkeys for you to ride." So these are for riding.