Chapter 28: The Book of Horses, Races and Shooting
It was narrated from Yahya bin 'Abbad bin 'Abdullah bin Az-Zubair, from his grandfather, that he used to say: "In the year of Khaibar, the Messenger of Allah allocated four shares to Az-Zubair bin Al-' Awwam: A share of Az-Zubair, a share for the relatives of Safiyyah bint 'Abdul-Muttalib, the mother of Az-Zubair, and two shares for the horse."
Sunan an-Nasa'i 3593