The Disciple from the 70 Onysimos in his youth was a servant of Philemon, a Christian of distinguished lineage, living in the city of Phrygian Colossa. Guilty of an offense against his master and fearing punishment, Saint Onysimos fled to Rome, but as a runaway slave he wound up in prison there. In prison he encountered the Apostle Paul held in chains, was enlightened by him and accepted holy Baptism. In prison Saint Onysimos served the Apostle Paul like a son. The Apostle Paul was personally acquainted with Philemon, and wrote him a letter filled with love, asking him to forgive the runaway slave and to accept him like a brother; he dispatched Saint Onysimos with this letter to his master, depriving himself of help, in which he was very much in need.
Saint Philemon, having received the letter, not only forgave Onysimos, but also dispatched him to sail back to Rome to the first-rank apostle. Saint Philemon was afterwards ordained bishop of the city of Gaza
After the death of the Apostle Paul, Saint Onysimos served the apostles until their end, and he was ordained bishop by them. After the death of the holy apostles he preached the Gospel in many lands and cities: in Spain, Carpetania, Colossa, Patras. In his old age, Saint Onysimos occupied the bishop's throne at Ephesus, in succession after the Disciple Timothy. When they took Ignatios the God-Bearer to Rome for execution, Bishop Onysimos came to meet with him with certain Christians, about which Saint Ignatios makes mention in his Epistle to the Ephesians.
During the reign of the emperor Trajan, Saint Onysimos was arrested and brought to trial before the eparch Tertillus. He held the saint for 18 days in prison, and then sent him for imprisonment to the city of Putiola. After a certain while, the eparch sent for the prisoner and, convincing himself that Saint Onysimos quite firmly confessed his faith in Christ, had him subjected to a fierce beating with stones, after which they beheaded the saint with a sword. A certain illustrious woman took the body of the martyr and placed it in a silver coffin. This was in about the year 109.