Musnad Ahmad 5:31

Sufyan narrated to us, from al-Zuhri, from al-Hasan and Abdullah, the two sons of Muhammad ibn Ali, from their father—and al-Hasan was the more pleasing of the two to us—that Ali said to Ibn Abbas: "The Messenger of Allah (peace and blessings of Allah be upon him) forbade the temporary marriage (mut'ah) and the meat of domestic donkeys at the time of Khaybar."