Slavery

Urge bond-slaves to be subject to their own masters in everything, to be well-pleasing, not argumentative, not pilfering, but showing all good faith that they may adorn the doctrine of God our Savior in every respect. (Titus 2:9–10)

The fifth category of believers about which Paul admonishes Titus is not based on age but on social standing. Douloi (bond-slaves) refers to slaves, those who were owned and controlled by their own masters.

The Roman Empire depended on bond-slaves for most of its labor, and they were an essential part of society and the economy. Many, if not most, slaves were abused and often brutalized. For even minor infractions, or simply for displeasing their owners in some way, they could be severely beaten or killed. Many of them, however, were given great responsibility and authority in running a household and sometimes a family farm or other business. Some of them—frequently those who were captured in war—were highly educated and cultured, in many cases having superior education to that of their owners. Slaves were allowed to marry and raise their own families, their children becoming slaves like their parents. A slave sometimes was given a small parcel of land on which to grow crops to feed his family and perhaps earn a small income...

http://www.macarthurcommentaries.com