And Allah the Exalted said (in Surah An-Nur) «والصالحين من عبادكم وإمائكم‏» "And those of your slaves and slave-girls who are fit (for marriage)..." And (in Surah An-Nahl) He said «عبدا مملوكا‏» "A slave owned..." And (in Surah Yusuf) He said «وألفيا سيدها لدى الباب‏» "And they (Yusuf and Zulaikha) found their master (the Aziz of Egypt) at the door." And Allah the Exalted said (in Surah An-Nisa) «من فتياتكم المؤمنات‏» "From among your believing slave-girls..." And the Prophet (peace and blessings be upon him) said, "Stand up for your chief (for Sa'd bin Mu'adh, may Allah be pleased with him)." And Allah the Exalted said in Surah Yusuf «اذكرني عند ربك‏» "(Yusuf said to his fellow prisoner:) Mention me to your master (the king)." And the Prophet (peace and blessings be upon him) (asked Banu Salamah:) "Who is your chief?"

Narrated `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."