"I beseech you concerning my son, whom I have begotten in chains, Onesimus, who was once useless to you, but is now useful to both you and me, whom I have sent back to you. But you, receive him, that is, my own heart, whom I wished to keep with me, so that he might serve me on your behalf in the chains of the gospel. " In wishing to obtain what he asks for, he now asserts that he is pleading not for Philemon's slave, but for his own son. And regarding that son whom he has begotten in the chains of the gospel, that is, which he endured for the sake of Christ's gospel: who, although he was once useless to his master (for a slave who steals and runs away harms no one but his own master), now on the contrary, by way of compensation for his usefulness to both his master and Paul, and to others through Paul, he deserves more love than he had previously deserved hatred. He says, "Who was useless to you at one time." "To you alone," he says, "not to others: but now it is useful to both me and you." It is useful to the master in that he could serve Paul as his master; Paul, however, is useful in this: that he could minister to him in the Gospel while he was being held in prison and chains. And at the same time we admire the magnanimity of the apostle and his fervent mind in Christ. He is held in prison, is bound in chains, is oppressed by the filth of his body, by separation from his loved ones, is cramped by penal darkness, and yet he feels no wrong, he is not tortured by pain, he knows nothing else but to think about the Gospel of Christ. He knew the slave, he knew the fugitive, he knew that he had been converted to the faith of Christ by a kidnapper. It is a great effort for a man to persevere in what he has begun. Therefore, he impresses, repeats, and urges his son and the son of bonds, and minister of the Gospel who is imprisoned, that Philemon, praised only in the preface, would not dare to refuse, lest he appear unworthy of his own praises. And what he says: "But you accept him, that is, my heart," this is what I said a little earlier, that "heart" signifies the internal affection of the heart and the full willingness from the soul, when everything that is in us is received from the one asking. But otherwise, all children are the parents' hearts.
Ver. 13. "Whom I would have retained with me, that in your stead he might have ministered unto me in the bonds of the Gospel."
Do you see after how much previous preparation, he has at length brought him honorably before his master, and observe with how much wisdom he has done this. See for how much he makes him answerable, and how much he honors the other. You have found, he says, a way by which you may through him repay your service to me. Here he shows that he has considered his advantage more than that of his slave, and that he respects him exceedingly.
Be careful to observe how much groundwork is necessary before Paul honorably brought Onesimus before his master. Observe how wisely he has done this. See for how much he makes Philemon answerable and how much he honors Onesimus. You have found, he says, a way by which you may through Onesimus repay your service to me. Here Paul shows that he has considered Philemon’s advantage more than that of his slave and that he deeply respects him.
Paul indicates that had he kept Onesimus, the result would have been that he could serve Paul as an extension of Philemon’s service and thus have been a source of gain for Philemon.
And he responds to a question, because it might be said if he is useful to you, why do you not keep him unto death? And he gives the reason for sending him back. First, he considers why he might keep him; second, why he rejects that idea: but I did not want to do anything without your counsel. Therefore, he says to Philemon who, although he is a great man, is accustomed to minister to the Apostle. Matthew 10:26: ‘On the contrary, whoever wishes to become great among you shall be your servant.’ Out of this confidence he proposed to keep him, so that in place of Philemon he might minister to him. I had wanted to keep him here with me that in your stead he might wait on me in my imprisonment for the Gospel. This was something especially needed since he was in chains for the sake of Christ, for one is provided for when he suffers for his master. The reason he rejected the idea was that he did not want to use another’s property without the owner’s knowledge.
[AD 420] Jerome on Philemon 1:10-13