Jerome — on Phlm 1:2 (Commentary on Philemon)

“Also to Apphia, the sister, not having anything false or imaginary in herself, and to Archippus, a fellow soldier whom I believe, along with Paul and Timothy, stood as a victorious opponent for Christ's name against adversaries and for this reason is now called a fellow soldier because he triumphed in the same battle and war. It is also written to the church that is in his house. But this [is] uncertain, whether [it refers to] the church which is in the house of Archippus, or [that] which is in the house of Philemon. But to me it seems that the person, to whom this letter is also addressed, should be referred not to Archippus, but to Philemon. For although Paul and Timothy jointly write to Philemon, Apphia, Archippus, and [the] church, yet in the following [part] it is [only] approved that only Paul write to Philemon, and speak of one with another. "I give thanks to my God always", "[and] making mention of thee." And you will find this way of writing in some of his letters: that although many [people] are introduced and mentioned in the preface, [only] one person, arguing, is [mentioned] throughout the whole body of the Epistle. That which the Apostle says when writing to the Galatians: that in Christ's faith there is no difference between a Gentile or a Jew, a man or a woman, a slave or a free man (Gal. 3:28): even in this place it is clear. For between two men and apostles, between Paul's co-worker and his comrade, the name of Apphia is inserted: in such a way that supported by such a company on both sides, it does not seem to indicate the order of sex but of merit.”