Manumission of Slaves
Bukhari :: Book 3 :: Volume 46 :: Hadith 723
Narrated Abu Musa Al-Ashari:
The Prophet said, "He who has a slave-girl and teaches her good manners and improves her education and then manumits and marries her, will get a double reward; and any slave who observes Allah's right and his master's right will get a double reward."