Abu Dawud Book 024, Hadith Number 3918.

Chapter : Sale of a slave who entered an agreement to purchase his freedom when the agreement is repudiated.

Narated By N/A : 'Urwah quoting 'Aisha said that Barirah came to her seeking her help to purchase her freedom, and she did not pay anything for her freedom. 'Aisha said to her: Return to your people; if they like that I make payment for the purchase of your freedom on your behalf and I shall have the right to inherit from you, I shall do so. Barirah mentioned it to her people, but they refused and said: If she wants to purchase your freedom for a reward from Allah, she may do so, but the right to inherit from you shall be ours. She mentioned it to the Apostle of Allah (may peace be upon him). The Apostle of Allah (may peace be upon. him) said: Purchase her (freedom) and set her free, for the right of inheritance belongs only to the one who set a, person free. The Apostle of Allah (may peace be upon him) then stood up and said: What is the matter with people who make conditions which are not in Allah's Book ! If anyone makes a condition which is not in Allah's Book, he has no right to it, even if he stipulates it hundreds of times. Allah's condition is more valid and binding."