Musnad Ahmad 33:785

'Affan narrated to us, Hammad ibn Salamah narrated to us, Abu al-Zubayr narrated to us, from Jabir ibn 'Abdullah, who said: "We slaughtered horses, mules, and donkeys on the day of Khaybar. The Messenger of Allah (ﷺ) forbade us from the mules and the donkeys, but he did not forbid the horses."