Sayyidah Maymunah (may Allah be pleased with her) said: I freed a slave girl of mine, and the Messenger of Allah (peace and blessings be upon him) came in to me, and I told him (peace and blessings be upon him) about freeing her. He (peace and blessings be upon him) said: "May Allah reward you. Had you given her to your maternal relatives, it would have been greater in reward for you."
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 20368