Maliks Muwatta Book 25, Hadith Number 15.
Yahya related to me from Malik that the best of what he had heard about horses, mules, and donkeys was that they were not eaten because Allah, the Blessed, the Exalted, said, “And horses, and mules and asses, for you to ride, and as an adornment. ” (Sura 16 ayat 8). He said, may He be Blessed and Exalted, “In cattle, some of them you ride, and some of them you eat.” (Sura 6 ayat 79). He said, the Blessed, the Exalted, “Mention Allah’s name over what He has provided you of cattle, and eat of them and feed the beggar (al-qani) and the suppliant (al-mutarr). (Sura 22 ayat 34).
Malik said “Allah mentioned horses, mules, and donkeys for riding and adornment, and He mentioned cattle for riding and eating.”
Malik said, “Al-qani also means the poor.”