Introductory. Paul writes from prison, sending greetings from himself and Timothy to Philemon a dear friend with whom he had worked probably during his stay in Ephesus Apphia (presumably Philemon's wife), and Archippus (Colossians 4:17, possibly his son) his spiritual comrade-in-arms, together with the brethren of their household. He is constantly hearing of the love and loyalty displayed by Philemon both towards the Lord Jesus and towards all the saints (Philemon 1:5): the hearts of God's people have been greatly cheered by his kindness, and the thought of one who in so true a sense is a brother has been a great joy and comfort to Paul (Philemon 1:7), so that it is with great thankfulness to God that he makes mention of Philemon in his prayers (Philemon 1:4), praying that the readiness to share with others which his faith has prompted may prove (increasingly) effectual, as he comes to fuller knowledge of all the good that there is among the Colossians, unto (a deeper experience of) Christ.
Philemon 1:2. our sister: i.e. in the faith (cf. mg.).