"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.
All bound slaves who flee to religious communities for refuge should be admonished and sent back to their masters in better dispositions, after the example of St. Paul who, although he had begotten Onesimus through the gospel, sent him back to Philemon. He had convinced Onesimus that the yoke of slavery, borne in a manner pleasing to the Lord, would render him worthy of the kingdom of heaven. Paul not only urged Philemon to annul the threat against his servant, being mindful of the Lord’s own words: “If you forgive men their offenses, your heavenly Father will forgive you also your offenses.” But also, in order that Philemon might be more kindly disposed toward Onesimus, Paul writes: “For perhaps he therefore departed for a season from you that you might receive him again forever; not as a servant, but instead of a servant, as a most dear brother.” If, however, it should be the case of a wicked master who gives unlawful commands and forces the slave to transgress the command of our Master, the Lord Jesus Christ, then it is our duty to oppose him, so that the name of God not be blasphemed by that slave’s performing an act displeasing to God.
Ver. 11. "Which in time past was to you unprofitable."
See how great is his prudence, how he confesses the man's faults, and thereby extinguishes his anger. I know, he says, that he was unprofitable.
"But now" he will be "profitable to you and to me."
He has not said he will be useful to you, lest he should contradict it, but he has introduced his own person, that his hopes may seem worthy of credit, "But now," he says, "profitable to you and to me." For if he was profitable to Paul, who required so great strictness, much more would he be so to his master.
See how great is Paul’s prudence, how he confesses the man’s faults and thereby extinguishes Philemon’s anger.… He has not said Onesimus will be useful to you, lest Philemon should refute this argument, but he has introduced his own person, that his hopes may seem worthy of trust. “But now,” he says, “profitable to you and to me.” For if Onesimus was profitable to Paul, who was quite strict, how more would he be so to his master.
I must stand in awe of the apostle’s greatness of soul here, as a man whose mind burns for Christ. He is held in prison, he is constrained by chains, in physical misery, separated from dear ones, plunged into prison darkness, yet he does not feel the injury, he is not crucified with sadness. Rather, he knows nothing else than to ponder the gospel of Christ.
He once was useless to you, that is, harmful in taking away your possession, but now, converted from evil to the state of virtue, he is useful for the service of God and man. 2 Timothy 2:21: ‘If anyone, therefore, has cleansed himself from these, he will be a vessel for honourable use...’ Proverbs 25:4: ‘Take away the rust from silver, and there shall come forth a most pure vessel.’
[AD 420] Jerome on Philemon 1:10-13