Onesimus was a Phrygian by birth and a slave to Philemon, a person of influence who had been converted to the faith by Saint Paul.
Philemon departed from Rome on a business trip and took with him Onesimus among others of his servants. There Onesimus stole money from his master and fled to Rome. Onesimus then attended the preaching of St. Paul while St. Paul was in prison, and was converted. He remembered that he had stolen from his master and from others and since he did not have anything left from the stolen money to return to the rightful owners, he was sorrowful and told St. Paul about that.
St. Paul comforted him (It is said that St. Paul came to consider him his own son.) and wrote an epistle to Onesimus' master, Philemon, informing him in it, that Onesimus became a follower of Christ saying, "I appeal to you for my son Onesimus, whom I have begotten while in my chains." St. Paul asked him to treat him gently and not to mind what he did but to consider what he lost as owed by the apostle.
When Onesimus took the epistle (accompanying Tychicus, the bearer of the letter) to his master Philemon, who was pleased by his faith and repentance and treated him as the apostle commanded. Furthermore, he offered him more money but St. Onesimus refused saying, "I am rich with Christ." Then he bid Philemon farewell and returned to Rome.
In Paulís Letter to the Colossians, Onesimus is again mentioned as accompanying Tychicus, the bearer of the letter.
St. Onesimus continued to serve St. Paul until St. Paul's martyrdom and was ordained a priest. After the martyrdom of St. Paul, the governor of Rome seized St. Onesimus and exiled him to one of the islands. He remained there preaching and baptizing the people of the island.
When the governor came to the island, he found him guiding the people to the belief in the Lord Christ. He was cruelly tortured in Rome, for eighteen days, by the governor of that city, who was especially infuriated by his preaching on the merit of celibacy. His legs and thighs were broken with bludgeons, and he was then stoned to death. His martyrdom occurred under Domitian in the year 90 or 95 A. D.
Saint Jerome and other Fathers believe he succeeded Saint Timothy as bishop of Ephesus.
THE EPISTLE OF ST. PAUL TO PHILEMON
Philemon, a noble citizen of Colossa, had a servant named Onesimus, who robbed him and fled to Rome, where he met St. Paul, who was then a prisoner there the first time. The apostle took compassion on him and received him with tenderness and converted him to the faith; for he was a Gentile before. St. Paul sends him back to his master with this Epistle in his favour: and though he beseeches Philemon to pardon him, yet the Apostle writes with becoming dignity and authority. It contains divers profitable instructions and points out the charity and humanity that masters should have for their servants.
Philemon Chapter 1
He commends the faith and charity of Philemon; and sends back to him his fugitive servant, whom he had converted in prison.
1:1. Paul, a prisoner of Christ Jesus, and Timothy, a brother: to Philemon, our beloved and fellow labourer,
1:2. And to Appia, our dearest sister, and to Archippus, our fellow soldier, and to the church which is in thy house.
1:3. Grace to you and peace, from God our Father and from the Lord Jesus Christ.
1:4. I give thanks to my God, always making a remembrance of thee in my prayers.
1:5. Hearing of thy charity and faith, which thou hast in the Lord Jesus and towards all the saints:
1:6. That the communication of thy faith may be made evident in the acknowledgment of every good work that is in you in Christ Jesus.
1:7. For I have had great joy and consolation in thy charity, because the bowels of the saints have been refreshed by thee, brother.
1:8. Wherefore, though I have much confidence in Christ Jesus to command thee that which is to the purpose:
1:9. For charity sake I rather beseech, whereas thou art such a one, as Paul, an old man and now a prisoner also of Jesus Christ.
1:10. I beseech thee for my son, whom I have begotten in my bands, Onesimus,
1:11. Who hath been heretofore unprofitable to thee but now is profitable both to me and thee:
1:12. Whom I have sent back to thee. And do thou receive him as my own bowels.
1:13. Whom I would have retained with me, that in thy stead he might have ministered to me in the bands of the gospel.
1:14. But without thy counsel I would do nothing: that thy good deed might not be as it were of necessity, but voluntary.
1:15. For perhaps he therefore departed for a season from thee that thou mightest receive him again for ever:
1:16. Not now as a servant, but instead of a servant, a most dear brother, especially to me. But how much more to thee, both in the flesh and in the Lord?
1:17. If therefore thou count me a partner, receive him as myself.
1:18. And if he hath wronged thee in any thing or is in thy debt, put that to my account.
1:19. I Paul have written it with my own hand: I will repay it: not to say to thee that thou owest me thy own self also.
1:20. Yea, brother. May I enjoy thee in the Lord! Refresh my bowels in the Lord.
1:21. Trusting in thy obedience, I have written to thee: knowing that thou wilt also do more than I say.
1:22. But withal prepare me also a lodging. For I hope that through your prayers I shall be given unto you.
1:23. There salute thee Epaphras, my fellow prisoner in Christ Jesus:
1:24. Mark, Aristarchus, Demas and Luke, my fellow labourers.
1:25. The grace of our Lord Jesus Christ be with your spirit. Amen.