Muwatta Imam Malik (Riwayat Ibn al-Qasim)

And with this same chain (it is narrated from Sayyidah Aisha, may Allah be pleased with her) that Barirah, may Allah be pleased with her, came and said: I have made a written contract with my owners for my freedom for nine (9) uqiyah of silver; I will give them one uqiyah each year. Please help me in this matter. So Sayyidah Aisha, may Allah be pleased with her, said: If your owners agree to this, I will pay them in cash, but the right of wala’ (allegiance) will be mine. Barirah went to her owners and told them this. They refused, so she came from her owners (to Aisha Siddiqa, may Allah be pleased with her), and the Messenger of Allah, peace and blessings be upon him, was also sitting there. She said: I told them this, but they refused and said that the right of wala’ would be theirs. When the Messenger of Allah, peace and blessings be upon him, heard this, he asked: (What is the matter?) Then Aisha, may Allah be pleased with her, informed him, so the Messenger of Allah, peace and blessings be upon him, said: “Take her and accept their condition of wala’, for the right of wala’ is only for the one who sets free.” So Aisha, may Allah be pleased with her, did so. Then the Messenger of Allah, peace and blessings be upon him, stood among the people, and after praising and glorifying Allah, he said: As for what follows, what is the matter with people who stipulate conditions that are not in the Book of Allah? Any condition that is not in the Book of Allah is invalid, even if there are a hundred such conditions. The decision of Allah is the most rightful, and the condition of Allah is the strongest, and the right of wala’ is only for the one who sets free.