Musannaf Ibn Abi Shayba 26:508

Waki' narrated to us, he said: Hisham ibn 'Urwah narrated to us, from his father, that a *mukātab* (a slave with a contract of manumission) of al-Zubayr married an *umm walad* (a slave woman who has borne a child to her master) of Rafi' ibn Khadij. He said: She bore children, then he (the *mukātab*) was emancipated. Al-Zubayr and Rafi' disputed regarding their *wala'* (patronage rights) before 'Uthman, and he judged the *wala'* to be for al-Zubayr.