I have often wondered why African (black slaves) would leave the religion of their people and take the religion of the slave masters. It seems just like their day job, those abused African people did not have much of a choice. But God did say it is ok to beat your slaves as long as they do not die within a couple of days (Genisis 22)
Make the the reward for obedience be posthumous, discourage knowledge and questioning ala The Garden Of Eden & Tower Of Babel, and accept your station in life ala the 10th commandment: Though shalt not covet, not to mention the positive refences to slavery in both the Old & New Testaments.