Musnad Abu Ya'la al-Mawsili 5:8

Hawthara ibn Ashras Abu 'Amir narrated to us, Hammad ibn Salama narrated to us, from Hisham ibn 'Urwa, from 'Urwa, that Ibn al-Zubayr said to him: "O father, I truly saw you charging on your chestnut horse on the day of the Trench." He said: "Did you see me, my son?" He said: "Yes." He said: "For the Messenger of Allah, may Allah bless him and grant him peace, was gathering for your father his parents on that day, saying: 'Shoot, may my father and mother be ransomed for you.'"