Musnad Abu Ya'la al-Mawsili 243:36

Abu Abd al-Rahman al-Allaf narrated to us, Abda narrated to us, Salih ibn Salih ibn Hayy al-Hamdani narrated to us, from al-Sha'bi, from Abu Burdah, from Abu Musa, from the Prophet (peace be upon him), who said: "Whoever has a slave girl, disciplines her and perfects her discipline, and teaches her and perfects her education, then frees her and marries her, he shall have two rewards. And any man from the People of the Scripture who believes in his prophet and believes in Muhammad, he shall have two rewards. And any slave who fulfills the right of Allah and the right of his masters, he shall have two rewards." Salih said: Al-Sha'bi said to me, "I have given it to you for nothing, even though a rider would have traveled for less than it to Medina."