To win Philemon’s willing acceptance of the runaway slave Onesimus, Paul writes very tactfully and in a light-hearted tone, which he creates with wordplay. The appeal is organised in a way prescribed by ancient Greek and Roman teachers: to build rapport, to persuade the mind, and to move the emotions.
Philemon was an inhabitant of Colosse, a person of some note and wealth, and a convert under the ministry of St. Paul. Onesimus was the slave of Philemon: having run away from his master, he went to Rome, where he was converted to the Christian faith, by the word as set forth by Paul, who kept him till his conduct proved the truth and sincerity of his conversion. He wished to repair the injury he had done to his master, but fearing the punishment his offence deserved might be inflicted, he entreated the apostle to write to Philemon. And St. Paul seems no where to reason more beautifully, or to entreat more forcibly, than in this epistle.Matthew Henry