Musannaf Ibn Abi Shayba 13:505

Abu Bakr narrated to us, he said: Ibn ‘Uyaynah narrated to us, from ‘Abdullah ibn Dinar, from Ibn ‘Umar, he said: The Messenger of Allah (may Allah bless him and grant him peace) forbade the selling of *wala’* (patronage rights) and the gifting of it.