Musnad Ahmad 33:298

Yahya ibn Sa'id narrated to us, from Ibn Jurayj, [who said]: Abu al-Zubayr informed me, [that he] heard Jabir ibn 'Abd Allah 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."