I do not issue orders to you, as if I were some great person. For though I am bound for the name [of Christ], I am not yet perfect in Jesus Christ. For now I begin to be a disciple, and I speak to you as fellow-disciples with me. For it was needful for me to have been stirred up by you in faith, exhortation, patience, and long-suffering. But inasmuch as love suffers me not to be silent in regard to you, I have therefore taken upon me first to exhort you that ye would all run together in accordance with the will of God. For even Jesus Christ, our inseparable life, is the [manifested] will of the Father; as also bishops, settled everywhere to the utmost bounds [of the earth], are so by the will of Jesus Christ.
Within reason, the master was perfectly entitled on the basis of his apostolic authority to tell his disciple what to do, but because Philemon was a good man, Paul makes an appeal.
Though Paul is writing to a layman, he nonetheless does not exert his apostolic authority in order to issue orders but respects Philemon as a faithful Christian and of the same age, one who is bound to Christ as he is.
Ver. 8. "Wherefore, though I might be much bold in Christ to enjoin you that which is convenient [befitting]."
Observe how cautious he is, lest any of the things which were spoken even from exceeding love should so strike the hearer, as that he should be hurt. For this reason before he says, "to enjoin you," since it was offensive, although, as spoken out of love, it was more proper to soothe him, yet nevertheless from an excess of delicacy, he as it were corrects it by saying, "Having confidence," by which he implies that Philemon was a great man, that is "You have given confidence to us." And not only that, but adding the expression "in Christ," by which he shows that it was not that he was more illustrious in the world, not that he was more powerful, but it was on account of his faith in Christ — then he also adds, "to enjoin you," and not that only, but "that which is convenient," that is, a reasonable action. And see out of how many things he brings proof for this. You do good to others, he says, and to me, and for Christ's sake, and that the thing is reasonable, and that love gives, wherefore also he adds,
I am writing to you because of the confidence I have in Christ Jesus, commanding you to do what is proper for the sake of love. I urge you even more, as one such as Paul, an old man and now also a prisoner of Christ Jesus. With many praises given to Philemon before him, considering the matter at hand, which would be both excellent and helpful to the requester, Paul was able to command rather than request. And this confidence came from the fact that whoever had done such great works for Christ could not be unequal to himself in other aspects. But he wishes to ask more than to command, with the authority of one asking for something great being proposed, through which both the Apostle begs, and the old man and prisoner of Jesus Christ. But that for which he is asking the whole time is: Onesimus, the servant of Philemon, he had fled and compounded some domestic item by theft: hence he had gone to Italy, so that he would not be easily apprehended in the near future, he had squandered his master's money through luxury. Lest anyone think this rashly, and that it is made up as we please, let him learn in the following. For Paul would never say: "If he has harmed you or owes anything, put it to my account: I, Paul, have written with my own hand; I will repay it." Nor would he become the surety of a lost thing, and if that which was lost had not been squandered. Therefore, when Paul was in prison in Rome because of the confession of Christ, he believed in Christ; and after being baptized by him, he wiped away the stains of his former life with worthy penance, to such an extent that the apostle himself became a witness of his conversion, who had once rebuked Peter for not walking rightly in the truth of the Gospel (Galatians 2). Therefore regarding sin and wrongdoing, in which he had injured the lord, he doesn't deserve forgiveness; however, regarding the testimony of the Apostle, who knows that he has been fully converted, he is burdened with great weight, since he is being asked who was once a fugitive slave and a robber, yet had become a minister of the Apostle. (And what other ministry does the Apostle have except the Gospel of Christ Jesus?) Now he is no longer to be forgiven as if by his master, but rather as if by a fellow servant and co-evangelist, as he too is a servant of Christ and a minister.
[AD 108] Ignatius of Antioch on Philemon 1:8