All who are forced to serve as slaves should consider their masters worthy of full respect. Then people will not speak evil things against God's name and against what we teach.
Some slaves have masters who are believers. They shouldn't show less respect for their masters just because they are believers. Instead, they should serve them even better. That's because those who benefit from their service are believers. They are loved by them. Teach the slaves those things. Try hard to get them to do them.