This young man was the subject of the letter of Saint Paul to Philemon, the shortest of the bank of Pauline letters that we have in the New Testament. As today’s martyrology entry remarks, Onesimus was a fugitive servant of Philemon, and was converted to Christianity by Saint Paul, who was then in prison. Paul sent him back to Philemon and demanded that Philemon demonstrate the charity that was due two Christian brothers, even when their social ranks were very different.

“Commemoration of Blessed Onesimus, whom the holy Apostle Paul received as a fugitive servant and whom, while in chains, he gave new birth to as a son in the Christian faith, as he himself wrote to [Onesimus’] lord Philemon.”

Roman martyrology, February the 15th

In the letter to Philemon, Paul began by commending Philemon for his charitable work, and then made this charity the basis of his request: that Onesimus be pardoned. Paul called Onesimus ‘the child of my imprisonment,’ for he had received the man into the Christian religion while himself suffering one of his frequent periods of imprisonment.

“I prefer to appeal to this charity of thine. Who is it that writes to thee? Paul, an old man now, and in these days the prisoner, too, of Jesus Christ; and I am appealing to thee on behalf of Onesimus, the child of my imprisonment. He did thee an ill service once; now, both to thee and to myself, he can be serviceable, and I am sending him back to thee; make him welcome, for my heart goes with him.”

Philemon, 9-12

So Philemon was requested that he accept back his servant, and to forgive all, for Onesimus was now more than a slave/servant: he was also a Christian and so a brother in Christ. 

“Do not think of him any longer as a slave; he is something more than a slave, a well loved brother, to me in a special way; much more, then, to thee, now that both nature and Christ make him thy own.”

Philemon 16

Paul promised to himself settle any debts that Onesimus may have with Philemon. If anything, this short letter demonstrates the Christian fellowship of those of different social strata, something that we may recognise from other letters that deal with good Christian behaviour in the milieu of the ancient world, where the relationship of slave to salve-owner was very much taken as a given and was yet beyond reform. Churchmen of the time, like Paul, would have had to beg in this fashion for the welfare of slaves. And the letter demonstrates the heart of the Apostle Saint Paul, trying his best to obtain a good result for one of his dear sons.