2 Kings 18; Philemon; Hosea 11; Psalms 132–134
IN THE FIRST CENTURY, a slave who ran away could legally be executed. A master might not enforce that punishment, but at the very least the runaway slave who was caught would face very brutal treatment.
Onesimus is a slave who has run away from Philemon. Somewhere along the line, Onesimus has been converted. Whether he sought out Paul before his conversion or after, Onesimus is now with Paul, probably in Rome. The apostle is in prison awaiting trial, and Onesimus, now a believer, is running errands for him and otherwise helping him out.
But Paul knows this cannot continue. The apostle himself could be charged with aiding and abetting a fugitive. Legally, even morally, Onesimus must go back to Philemon and square things. But where is the morality in Roman slavery itself?
So Paul writes to Philemon and Apphia, knowing they are Christians, presumably well-to-do, with a home big enough to house the church where they live. The letter is a masterpiece of firm, godly diplomacy.
Paul commends Philemon for his love and encouragement (v. 7). He mentions that he could simply order him to take certain actions (v. 8), yet he prefers to appeal to him "as Paul—an old man and now also a prisoner of Christ Jesus" (v. 9) so that Philemon will act out of love. Only then does he mention Onesimus, and state what the appeal consists in. Paul wants Philemon to take back Onesimus, whom Paul characterizes as his "son," now a "useful" person (which is what the name Onesimus means), and so loved by the apostle that he is Paul's "very heart" (vv. 10–12). Paul would have been happy to keep him, but would not do anything without Philemon's "consent" (v. 14). Of course, Onesimus had run away, but regardless of how reprehensible that act had been, in the larger scheme of things "perhaps the reason he was separated from you for a little while [a convenient passive!] was that you might have him back for good—no longer as a slave, but better than a slave, as a dear brother" (vv. 15–16). Surely he will therefore be dear to Philemon, "both as a man and as a brother in the Lord" (v. 16).
So Philemon is to welcome back Onesimus as he would welcome the apostle himself (v. 17), who hopes to come soon on a visit that will check up on things (v. 22). Apparently Onesimus stole from Philemon when he left: Paul says he will gladly repay the full amount—though Paul gently reminds Philemon of the supreme debt he owes to the man who brought him the Gospel.
Nothing can destroy brutal relationships faster than the Gospel rightly applied.