Musannaf Ibn Abi Shayba 35:241

Shababah ibn Sawwar narrated to us, from Malik ibn Anas, from Nafi’, from Ibn ‘Umar, who said: ‘Aisha wanted to purchase Barirah. They said: “Will you purchase her on the condition that her wala’ (right of inheritance/patronage) is for us?” She mentioned that to the Prophet, may Allah bless him and grant him peace. The Messenger of Allah, may Allah bless him and grant him peace, said: “That does not harm you regarding her, for the wala’ belongs only to the one who emancipates.” And it was mentioned that Abu Hanifah said: “This purchase is corrupt; it is not permissible.”