Musnad Ahmad 1167:72

Waki’ narrated to us, he said: Hisham narrated to us, from Fatimah bint al-Mundhir, from Asma’ bint Abi Bakr, she said: "We slaughtered a horse during the time of the Messenger of Allah, peace and blessings of Allah be upon him, and we ate its meat," or "from its meat."