Onesimus was one of the Seventy. He was a slave of Philemon but transgressed against his master and fled to Rome. There he heard the Gospel from the Apostle Paul and was baptized. Since the Apostle Paul had earlier converted Philemon to the true Faith, he reconciled the two of them – Philemon and Onesimus, master and slave – writing a special epistle to Philemon. It is one of the most touching compositions in Holy Scripture. I beseech thee for my son Onesimus, whom I have begotten in my bonds … For perhaps he therefore departed for a season, that thou shouldest receive him for ever. Not now as a servant, but above a servant, a brother beloved, specially to me (Philemon 1:10, 15, 16). Indeed, moved by this letter, Philemon received Onesimus as a brother, freeing him from slavery. Later Onesimus was consecrated a bishop by the apostles themselves, and he accepted the Episcopal throne at Ephesus at the death of the Apostle Timothy. This is evident from the Epistle of Ignatius the God-bearer. At the time of Trajan’s persecution, Onesimus, already an old man, was arrested and brought to Rome. In Rome Onesimus gave an account of himself before the judge Tertulus, and he was imprisoned and finally beheaded. A wealthy woman removed his body, placed it in a silver coffin and buried it honorably, in the year 109.
Source: St. Nikolai Velimirovic, The Prologue of Ohrid – Volume One.
O Holy Apostle Onesimus, intercede to our merciful God, that He may grant our souls forgiveness of sins.