Sayyidah Barirah (may Allah be pleased with her) said: Three sunnahs (were established) in my case: Meat was given to me as charity, and I gave it as a gift to Sayyidah Aishah (may Allah be pleased with her). She kept it aside until the Messenger of Allah (peace and blessings be upon him) came in, and he said: "What is this meat?" She said: This is meat that was given to Barirah as charity, and she gave it to us as a gift. He (peace and blessings be upon him) said: "It is charity for Barirah and a gift for us." She said: And I had made a contract of manumission (mukatabah) for nine awqiyah of silver. Sayyidah Aishah (may Allah be pleased with her) said: If they wish, I will count out the whole amount to them in a single payment. I said: They say: (Not) unless the wala' is stipulated for them. So the Prophet (peace and blessings be upon him) said: "Stipulate it, stipulate it, for the wala' belongs only to the one who sets free." She said: So I was set free, and I was given the choice.
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 20895