Once upon a time there was a slave with a very common slave name—Onesimus. The name means “useful,” and people “used” slaves to meet their own needs and goals. Slaves who ran away were sent back to their owners for punishment. But Roman law also allowed slaves to run away to special temples, or to seek the intervention of an influential friend of the owner, if they anticipated harsh and severe punishment for some reason. Well, this particular Onesimus ran away from a man named Philemon, and ran to someone he believed would have influence with him. He ran to Paul.
Now Paul was in prison at the time. He was there for preaching the Gospel. So Onesimus was not only exposed to that Gospel through his association with Paul, he became a convert. And what that meant, in Paul’s view, was that Onesimus was now an equal. He was not just “equal in the eyes of God” he was equal in practical, concrete terms. He could no longer be treated as a slave. He was free.
Under Roman law, however, Onesimus was Philemon’s “property.” Yet since both were baptized into Christ, they were now brothers. They were equals. And as Paul prepared to send Onesimus back to Philemon, which he was bound to do under Roman law, he wrote a letter to Philemon explaining the situation in coaxing terms.