If, therefore, thou holdest me to be thy associate. Here he lowers himself still further, by giving up his right and his honor to a runaway, and putting him in his own room, as he will shortly afterwards offer himself to be his cautioner. He reckoned it to be of vast importance that Onesimus should have a mild and gentle master, that immoderate severity might not drive him to despair. That is the object which Paul toils so earnestly to accomplish. And his example warns us how affectionately we ought to aid a sinner who has given us proof of his repentance. And if it is our duty to intercede for others, in order to obtain forgiveness for those who repent, much more should we ourselves treat them with kindness and gentleness.

If there count me therefore a partner - The word rendered "partner" (κοινωνὸς koinōnos, means "a partaker, a companion." The idea in the word is that of having something in common (κοινὸς koinos) with any one - as common principles; common attachments; a common interest in an enterprise; common hopes. It may be applied to those who hold the same principles of religion, and who have the same hope of heaven, the same views of things, etc. Here the meaning is, that if Philemon regarded Paul as sharing with him in the principles and hopes of religion, or as a brother in the gospel so that he would receive him, he ought to receive Onesimus in the same way. He was actuated by the same principles, and had the same hopes, and had a claim to be received as a Christian brother. His receiving Onesimus would be interpreted by Paul as proof that he regarded him as a partaker of the hopes of the gospel, and as a companion and friend. For a plea in behalf of another, strongly resembling this, see Horace, Epis. Lib. 1, Ephesians. 9.

If thou count me therefore a partner - If thou dost consider me as a friend; if I have still the place of a friend in thy affection, receive him as myself; for, as I feel him as my own soul, in receiving him thou receivest me.
There is a fine model of recommending a friend to the attention of a great man in the epistle of Horace to Claudius Nero, in behalf of his friend Septimius, Epistolar. lib. i., Ep. 9, which contains several strokes not unlike some of those in the Epistle to Philemon. It is written with much art; but is greatly exceeded by that of St. Paul. As it is very short I shall insert it: -
Septimius, Claudi, nimirum intelligit unus,
Quanti me facias; nam cum rogat, et prece cogit
Scilicet, ut tibi se laudare, et tradere coner,
Dignum mente domoque legentis honesta
Neronis, Munere cum fungi propioris censet amici;
Quid possim videt, ac novit me valdius ipso.
Multa quidem dixi, cur excusatus abirem:
Sed timui, mea ne finxisse minora putarer,
Dissimulator opis propriae, mihi commodus uni.
Sic ego, majoris fugiens opprobria culpae,
Frontis ad urbanae descendi praemia.
Quod si Depositum laudas, ob amici jussa, pudorem;
Scribe tui gregis hunc, et fortem crede bonumque.
"O Claudius Septimius alone knows what value thou hast for me; for he asks and earnestly entreats me to recommend him to thee, as a man worthy of the service and confidence of Nero, who is so correct a judge of merit. When he imagines that I possess the honor of being one of thy most intimate friends, he sees and knows me more particularly than I do myself. I said indeed many things to induce him to excuse me; but I feared lest I should be thought to dissemble my interest with thee, that I might reserve it all for my own advantage. Therefore, in order to shun the reproach of a greater fault, I have assumed all the consequence of a courtier, and have, at the request of my friend, laid aside becoming modesty; which if thou canst pardon, receive this man into the list of thy domestics, and believe him to be a person of probity and worth."
This is not only greatly outdone by St. Paul, but also by a letter of Pliny to his friend Sabinianus, in behalf of his servant, who, by some means, had incurred his master's displeasure. See it at the conclusion of these notes (Plm 1:25 (note)).

If thou count me therefore a partner,.... A companion and friend, who reckon each other's affairs and interest their own: the word answers to a word often used in Talmudic writings, for an associate of the doctors or wise men: here it may mean also a partner both in grace, and in the ministry; one that shared in the same gifts and graces of the Spirit of God, and one that was to be a partaker of the inheritance with the saints in light: now if Philemon reckoned the apostle such an one, as he doubtless did, as being engaged in the same common cause, and a partaker of the same common faith, and interested in the same common salvation; then he entreats him on account of Onesimus, in the following manner,
receive him as myself; intimating, that he was as dear to him as himself; that he loved him as his own soul; and that he should take whatever respect and affection were shown to him as done to himself; and that he would have him receive him into his house, his heart and affections, as he would receive him the apostle himself, should he come to him.

a partner--in the Christian fellowship of faith, hope, and love.
receive him as myself--resuming "receive him that is mine own bowels."

If thou accountest me a partner - So that thy things are mine, and mine are thine.