Al-Aswad (may Allah have mercy on him) narrates that Sayyidah Aishah (may Allah be pleased with her) said: I bought Barirah, and her people stipulated the wala'. I mentioned this to the Prophet (peace and blessings be upon him), and he (peace and blessings be upon him) said: "Free her, for the wala' belongs to the one who frees." So I freed her, and the Messenger of Allah (peace and blessings be upon him) called her and gave her the choice regarding her husband. She said: Even if he gave me such-and-such, I would not stay with him. So she chose herself (separation), and her husband was free.
The narration of al-Bukhari in the Sahih from Uthman bin Abi Shaybah is without the words: "and her husband was free"; this is the statement of al-Aswad. Al-Bukhari said: The statement of al-Aswad is munqati' (disconnected), and the statement of Ibn Abbas (may Allah be pleased with them both), "I saw him as a slave," is more authentic.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب المكاتب / 21736