Musannaf Ibn Abi Shayba 13:508

Abu Bakr narrated to us, he said: Ibn ‘Uyaynah narrated to us, from Ibn Abi Najih, from Mujahid, he said: ‘Ali said: "The *wala’* (right of inheritance/patronage) is in the status of an alliance; it is not sold and it is not gifted. Leave it where Allah has placed it."