Musnad Ahmad 1153:141

Abu Mu'awiyah narrated to us, Al-A'mash narrated to us, from Ibrahim, from Al-Aswad, from Aisha, who said: The husband of Barirah was a free man. When she was emancipated—and he said once: "When she became free"—the Messenger of Allah (peace and blessings of Allah be upon him) gave her the choice, and she chose herself. She said: Her family wanted to sell her and stipulate the right of inheritance (al-wala'). She said: So I mentioned that to the Prophet (peace and blessings of Allah be upon him), and he said: "Buy her and emancipate her, for the right of inheritance belongs to the one who emancipates."