Sahih Bukhari
Sahih Bukhari Volume 003, Book 046, Hadith Number 726.
Hadith Section/Book: Sahih Bukhari Sahih Bukhari Book 46. Manumission Of Slaves
Narated By 'Abdullah : The Prophet said, "If a slave serves his Saiyid (i.e. master) sincerely and worships his Lord (Allah) perfectly, he will get a double reward."