The word slave makes one feel sick on the inside. Just the thought that one human being would force another human being into slavery for his own personal gain is sickening. Yet, that is what was happening in the Roman Empire during the early days of Christianity, affecting the lives of many believers in Jesus. As a result, Paul addressed the issue in some of his letters, such as in Ephesians 6:5-9.
Slaves, obey your earthly masters with respect and fear, and with sincerity of heart, just as you would obey Christ.