Not quite. Slavery was a common practice in the Old Testament, as well as the Roman Empire. God's purposes in the Old Testament are to grant a homeland to the descendants of Abraham in order to be a blessing to all people. In that day, slavery was the result of war, which is how the Israelites gained their home. In the New Testament, slavery is not condoned or supported. Jesus's message and sacrifice was for all people, creating a degree of equality that had never been seen before. Why would slaves have to be told to obey their masters? They were already doing that. Telling them to do so implies that some event has occurred that makes that necessary. The gospel freed people, but in order to show the radical nature of Christianity, slaves were exhorted not to rise up against their masters. It was to demonstrate the peacefulness and nonviolence of this new teaching.