Barirah came to Ayesha seeking help in paying off her writ of manumission. Ayesha said to her, "Go back to your owners, and if they agree that I pay off your contract on the condition that your right of allegiance belongs to me, I will do so."Barirah mentioned this to her owners, but they refused and said, "If she wishes to do this for you as a charitable act, let her do so, but your right of allegiance will remain with us."Ayesha mentioned this to the Messenger of Allah ﷺ, and he said to her, "Buy her and free her, for the right of allegiance belongs to the one who frees the slave."Then the Messenger of Allah ﷺ said, "What is the matter with people who stipulate conditions that are not in the Book of Allah? Whoever stipulates a condition not found in the Book of Allah has no claim to it, even if he stipulates a hundred conditions. The condition set by Allah is more deserving of being followed and more binding."
أخبرنا قتيبة بن سعيد قال حدثنا الليث عن ابن شهاب عن عروة
أن بريرة جاءت عائشة تستعينها في كتابتها شيئا فقالت لها عائشة ارجعي إلى أهلك فإن أحبوا أن أقضي عنك كتابتك ويكون ولاؤك لي فعلت فذكرت ذلك بريرة لأهلها فأبوا وقالوا إن شاءت أن تحتسب عليك فلتفعل ويكون لنا ولاؤك فذكرت ذلك لرسول الله ﷺ فقال لها رسول الله ﷺ ابتاعي وأعتقي فإن الولاء لمن أعتق ثم قال رسول الله ﷺ ما بال أقوام يشترطون شروطا ليست في كتاب الله فمن اشترط شيئا ليس في كتاب الله فليس له وإن اشترط مائة شرط وشرط الله أحق وأوثق
Bukhari narrated it, Mukatab, chapter on what conditions are permissible for the mukatab, etc., no. 2561, and Muslim, Manumission (Itq), chapter explaining that guardianship (wala) belongs to the one who freed the slave, no. 6/1504, from Qutayba, with this wording. It is also found in Kubra, no. 6251.