St. Onesimus was a slave to Philemon, a powerful man who had been converted by St. Paul. Onesimus offended Philemon, and fled to escape his retribution. He met St. Paul in a Roman prison, and was baptized shortly afterwards. 

Paul sent a letter to Philemon asking for Onesimus’ freedom, so that Onesimus could become his assistant. In the Epistle to Philemon, he entreats Philemon to accept Onesimus “no longer as a slave, but more than a slave, a brother, beloved especially to me.” 

Philemon pardoned Onesimus, and he began serving Paul. Paul made him, with Tychicus, the bearer of his Epistle to the Colossians. 

Later, according to St. Jerome and others, Onesimus became an ardent preacher of the Gospel. He succeeded St. Timothy as bishop of Ephesus. 

When Onesimus’ preaching about the merits of celibacy angered a governor of Rome, he was seized and tortured for 18 days. Both his legs and thighs were broken, and he was eventually stoned to death in the year 90.