I beseech thee for my son Onesimus - It is evident from this that Onesimus was converted by St. Paul while he was prisoner at Rome, and perhaps not long before he wrote this epistle.
I beseech thee for my son Onesimus - That is, my son in the gospel; one to whom I sustain the relation of a spiritual father; compare the notes at 1 Timothy 1:2. The address and tact of Paul here are worthy of particular observation. Any other mode of bringing the case before the mind of Philemon might have repelled him. If he had simply said, “I beseech thee for Onesimus;” or, “I beseech thee for thy servant Onesimus,” he would at once have reverted to his former conduct, and remembered all his ingratitude and disobedience. But the phrase “my son,” makes the way easy for the mention of his name, for he had already found the way to his heart before his eye lighted on his name, by the mention of the relation which he sustained to himself. Who could refuse to such a man as Paul - a laborious servant of Christ - an aged man, exhausted with his many sufferings and toils - and a prisoner - a request which he made for one whom he regarded as his son? It may be added, that the delicate address of the apostle in introducing the subject, is better seen in the original than in our translation. In the original, the name Onesimus is reserved to come in last in the sentence. The order of the Greek is this: “I entreat thee concerning a son of mine, whom I have begotten in my bonds - Onesimus.” Here the name is not suggested, until he had mentioned that he sustained to him the relation of a son, and also until he had added that his conversion was the fruit of his labors while he was a prisoner. Then, when the name of Onesimus is mentioned, it would occur to Philemon not primarily as the name of an ungrateful and disobedient servant, but as the interesting case of one converted by the labors of his own friend in prison. Was there ever more delicacy evinced in preparing the way for disarming one of prejudice, and carrying an appeal to his heart?
Whom I have begotten in my bonds - Who has been converted by my efforts while I have been a prisoner. On the phrase “whom I have begotten,” see 1 Corinthians 4:15. Nothing is said of the way in which he had become acquainted with Onesimus, or why he had put himself under the teaching of Paul; see the introduction, Section 2. See (3) below.