Musannaf Ibn Abi Shayba 26:494

Waki’ narrated to us, he said: Shu’bah narrated to us, he said: I asked al-Hakam, Hammad, and Iyas ibn Mu’awiyah ibn Qurrah about a woman who emancipated a slave of hers, then she died and left behind her father and her son. They both (al-Hakam and Hammad) said: The *wala’* (right of inheritance/patronage) belongs to the son. And Iyas said: The *wala’* belongs to her children as long as any of them remain.