Sayyidah Maymunah (may Allah be pleased with her) freed a slave girl of hers without seeking the permission of the Messenger of Allah (peace and blessings be upon him). When her day came, she said: O Messenger of Allah, did you know that I have freed my slave girl so-and-so? He (peace and blessings be upon him) said: "Have you done so?" She said: Yes. He (peace and blessings be upon him) said: "Had you given her to your maternal relatives, it would have been greater in reward for you."
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 20369