Musnad Ahmad 1153:1768

Waki’ narrated to us, he said: Hisham narrated to us, from his father, from ‘Aisha, that Barirah came to her while she was a *mukatabah* (a slave who had entered into a contract of manumission), and her people had contracted her for nine *awqiyah* (of silver). She said to her: "If your people wish, I will count it out for them in one payment, and the *wala’* (right of inheritance/patronage) will be mine." She went to her people and mentioned that to them, but they refused, except that they stipulated the *wala’* for themselves. She said: So ‘Aisha mentioned that to the Prophet, peace and blessings of Allah be upon him, and he said: "Do it." So she did it. Then the Prophet, peace and blessings of Allah be upon him, stood and addressed the people. He praised Allah and extolled Him, then said: "What is the matter with people who stipulate conditions that are not in the Book of Allah?" He said: "Every condition that is not in the Book of Allah is void. The Book of Allah is more worthy, and His condition is more binding, and the *wala’* belongs to the one who emancipated."