Onesimus was a slave who once belonged to Philemon. For one reason or another Onesimus has left Philemon to be with Paul and is now returning. Paul writes to Philemon from prison to ask that he receive Onesimus back into his household.
It is not clear why Onesimus has left Philemon. Some commentators have come to the conclusion that Onesimus has run away—perhaps in an attempt to gain his freedom or perhaps to escape harsh treatment by Philemon. There is a suggestion that Onesimus may have harmed Philemon in some way—perhaps by stealing or perhaps causing destruction of property. Another possibility is that Philemon has loaned out Onesimus to Paul to assist him in his journeys. Whatever the case may be, now that Paul is a prisoner he no longer has need for Onisemus and wants Philemon to take him back.
It must be said that this letter to Philemon is in no way an argument for or against slavery. That is not the issue here and Paul takes no position on the institution of slavery. In other places Paul makes what appear to be supportive comments on slavery, saying that slaves should honorably obey their masters while masters must be just and fair with their slaves [see Colossians 3:22-4:1]. Here Paul merely acknowledges slavery as a normal social convention while pointing out that because Onesimus has become a follower of Christ he has become more than just a slave.
Paul reminds Philemon that Onesimus was once useless. Onesimus is a Greek name that was common among slaves and means “useful”—so Paul is making a play on the name. Maybe Onesimus had done something wrong to Philemon. Maybe he simply was not a productive slave—which may be why Philemon was willing to part with him. Either way, Paul is now sending Onesimus back to Philemon better than he was before. Now Onesimus is a follower of Christ. Now Onesimus really is useful. Paul insists that Philemon treat him as a member of the household of faith.
The issue in this letter is reconciliation. Paul wants Philemon and Onesimus to be reconciled—to put aside whatever barriers there were between them. Paul even goes so far as to offer to pay any debts Onesimus may have incurred. Reconciliation—that is what it truly means to be useful. It is useful to overcome obstacles and put aside barriers. It is useful to pay the debts of others and to welcome others into the community of faith. It is useful to do away with animosity and hatred because then we can be productive and fruitful. It is useful for followers of Christ to work for reconciliation because that is what Christ did for us.
Grace and Peace, Pastor Rik