Ayesha reported,

Barirah came to me and said, "My masters have made a contract with me to buy my freedom for nine ounces of silver, payable over nine years, one ounce each year. Help me."I said to her, "If your masters agree that I pay them the entire sum at once, set you free, and keep the right of guardianship for myself, I will do it."She mentioned this to her masters, but they refused unless the right of guardianship remained with them. She came back and told me what they had said. I rebuked her sharply, but she replied, "By Allah, no, that will not happen."The Messenger of Allah ﷺ heard this and asked me about it, so I told him what had taken place. He said, "Buy her and set her free, and let them stipulate whatever they wish about guardianship, for guardianship belongs only to the one who frees the slave." So I did.Later that evening, the Messenger of Allah ﷺ addressed the people. He praised Allah and glorified Him as He deserves, then said, "To proceed. What is the matter with people who lay down conditions not found in the Book of Allah? Any condition not found in the Book of Allah is invalid, even if there are a hundred such conditions. The decree of Allah is more deserving to be followed, and the condition of Allah is more binding. What is the matter with Some men among you who say to another, 'Free so-and-so, and the right of guardianship will be mine'? Guardianship belongs only to the one who frees the slave."

و حدثنا أبو كريب محمد بن العلاء الهمداني حدثنا أبو أسامة حدثنا هشام بن عروة أخبرني أبي

عن عائشة قالت

دخلت علي بريرة فقالت إن أهلي كاتبوني على تسع أواق في تسع سنين في كل سنة أوقية فأعينيني فقلت لها إن شاء أهلك أن أعدها لهم عدة واحدة وأعتقك ويكون الولاء لي فعلت فذكرت ذلك لأهلها فأبوا إلا أن يكون الولاء لهم فأتتني فذكرت ذلك قالت فانتهرتها فقالت لا ها الله إذا قالت فسمع رسول الله ﷺ فسألني فأخبرته فقال اشتريها وأعتقيها واشترطي لهم الولاء فإن الولاء لمن أعتق ففعلت قالت ثم خطب رسول الله ﷺ عشية فحمد الله وأثنى عليه بما هو أهله ثم قال أما بعد فما بال أقوام يشترطون شروطا ليست في كتاب الله ما كان من شرط ليس في كتاب الله عز وجل فهو باطل وإن كان مائة شرط كتاب الله أحق وشرط الله أوثق ما بال رجال منكم يقول أحدهم أعتق فلانا والولاء لي إنما الولاء لمن أعتق