Abd al-Rahman bin al-Qasim (may Allah have mercy on him) narrates from his father that Sayyidah Aishah (may Allah be pleased with her) bought Sayyidah Barirah (may Allah be pleased with her) from some people of the Ansar, and they stipulated (that they would keep) the wala' (right of inheritance from the freed slave). The Messenger of Allah (peace and blessings be upon him) said: "The wala' belongs to the one who frees." The Messenger of Allah (peace and blessings be upon him) gave her the choice (regarding her marriage), and her husband was a slave. She gave Sayyidah Aishah (may Allah be pleased with her) some meat as a gift, and the Messenger of Allah (peace and blessings be upon him) said: "It is charity for her (Barirah) and a gift for us."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الهبات / 12046