Sunan Ibn Majah, Chapter: The Chapters on Marriage

that the Messenger of Allah (saw) said: 'Whoever has a slave woman and teaches her good manners and educates her, then sets her free and marries her, will have two rewards. Any man from among the People of the Book who believed in his Prophet (saw) and believed in Muhammad will have two rewards. Any slave who does his duty towards Allah and towards his masters will have two rewards." (Sahih) (one of the narrators) Salih said: "Shabi said: 'I have given this (Hadith) to you for little effort on your part. A rider would travel to Al-Madinah for less than this.' "