Sahih Muslim
The Book of Games and the Animals which May be Slaughtered and the Aninals that Are to be Eaten (Kitab-us-Said wal-Dhabaih wa ma Yukalu min Al-Hayawan)
Book Number: 021 / Hadith Number: 4781
Asma' reported: We slaughtered a horse and ate it during the lifetime of Allah's Messenger (may peace be upon him).