Musnad Ahmad 27:1470

Ishaq ibn Isa narrated to us, Malik informed me, from Nafi, from Ibn Umar, that Aisha wanted to buy a slave girl to emancipate her. Her family said: "We will sell her to you on the condition that her wala (right of inheritance/patronage) is for us." She mentioned that to the Messenger of Allah, peace and blessings of Allah be upon him, and he said: "Do not let that prevent you, for the wala belongs to the one who emancipates."