Mukhtasar Bukhari (Abridged) 83 — Man teaching his slave and family

Narrated from Sayyiduna Abu Musa (may Allah be pleased with him) that the Messenger of Allah (peace and blessings of Allah be upon him) said: There are three persons for whom there is a double reward: (1) A person who is from the People of the Book, who believed in his own prophet and (then) also believed in Muhammad (peace and blessings of Allah be upon him); (2) A slave, when he fulfills the rights of Allah and the rights of his masters; (3) A person who has a slave-girl, teaches her good manners and gives her excellent training, and gives her good and excellent education, then sets her free and marries her, so for him there is a double reward.