Musnad Ahmad 788:48

'Abd al-Rahman narrated to us, from Sufyan, from Salih al-Thawri, from al-Sha'bi, from Abu Burdah, from Abu Musa, from the Prophet, peace and blessings of Allah be upon him, who said: "Whoever has a slave girl and teaches her, and perfects her teaching, and disciplines her, and perfects her discipline, then emancipates her and marries her, he shall have two rewards. And a slave who fulfills the right of Allah, the Almighty and Majestic, and the right of his masters. And a man from the People of the Book who believed in what 'Isa (Jesus) brought, and what Muhammad, peace and blessings of Allah be upon him, brought, he shall have two rewards."