This question already has an answer here:
Is it ok to have slavery according to bible?
Servants, be subject to your masters with all fear; not only to the good and gentle, but also to the froward.
For this is thankworthy, if a man for conscience toward God endure grief, suffering wrongfully.
For what glory is it, if, when ye be buffeted for your faults, ye shall take it patiently? but if, when ye do well, and suffer for it, ye take it patiently, this is acceptable with God.