Paul’s epistle to Philemon is one of the few books in the NT whose authenticity has hardly ever been doubted. Paul mentions his own name three times in this his shortest epistle (verses 1.9.19). Twice he speaks of being a prisoner of Jesus Christ. He mentions this also in his other “prison epistles” (Ephesians, Philippians and Colossians).
Philemon is not mentioned anywhere else in the NT. The epistle shows that he was a believing Christian and an esteemed acquaintance of the Apostle. The Epistle is addressed to Philemon, with the church in his house, and to sister Apphia and Archippus. Archippus is also mentioned in Colossians 4:17. This shows that Philemon lived in Colossae. In Colossians 4:7-9 we learn that Onesimus was from Colossae also.
The Epistle was written at the same time as the Epistle to the Colossians, that is 61 to 62 AC, from Rome. In both Epistles Paul mentions his imprisonment and gives greetings from Ephaphras, Marcus, Aristarcus, Demas and Luke. In Colossians the believers are informed that Tychicus, who was the deliverer of the Epistle, was accompanied by Onesimus.
Tertullian (around 160 to 220 AC) and the Muratori Canon (end of 2 nd century) testify that the Epistle was written by Paul.
Slavery was a fixed component of the social and governmental order in antiquity. A slave was considered a “thing” and therewith the sole property of his proprietor. A run-away-slave as Onesimus was had to fear most severe punishment.
Among the first Christians there were many slaves. This is evident from various passages in the NT (1 Corinthians 7:21-24; 1 Corinthians 12:13; Galatians 3:28; Ephesians 6:5-8; Colossians 3:22-25 : 1 Timothy 6:1-2; Titus 2:9-10). Although slavery was a consequence of man’s sin and therefore not according to the will of God, slaves did not receive outward liberty from their often hard fate when they believed in the Saviour Jesus Christ.
They were however encouraged to be faithful witnesses for God and His grace through their new life in Christ; and even more so if their masters were not Christians. God does not want to change the world by revolution but by leading people from darkness into His wonderful light.
This is why Paul does not question Philemon’s authority over Onesimus, his slave. But Paul appeals to Philemon’s heart in verses 15 to 21 and this may have produced Onesimus’ liberation (compare 1 Corinthians 7:20-24).