Musnad Ahmad 33:358

Muhammad ibn Bakr narrated to us, Ibn Jurayj informed us, and Hajjaj, from Ibn Jurayj, Abu al-Zubayr informed me that he heard Jabir ibn Abdullah being asked about riding the sacrificial animal (hadi). He said: I heard the Messenger of Allah, peace and blessings of Allah be upon him, say: "Ride it in a reasonable manner when you are compelled to do so, until you find a mount."