Here Paul shifts the focus onto yet another relationship in which to demonstrate the gospel. He addresses servants by encouraging them to obey their masters as they would Christ. He then goes on to address masters by pointing out that servants have no less value than they do and he urges them to treat their servants well. The same applies to our employer-employee relationships today.
Now that we belong to God, whether we are in situations of justice or injustice, we are called to serve others with sincere hearts as we serve Jesus. By doing this we are participating in the will of God and as a result will be rewarded as good and faithful servants for honoring Christ and displaying his glory.
Bondservants, obey your earthly masters with fear and trembling, with a sincere heart, as you would Christ, not by the way of eye-service, as people-pleasers, but as bondservants of Christ, doing the will of God from the heart, rendering service with a good will as to the Lord and not to man, knowing that whatever good anyone does, this he will receive back from the Lord, whether he is a bondservant or is free. Masters, do the same to them, and stop your threatening, knowing that he who is both their Master and yours is in heaven, and that there is no partiality with him.