Thomas Aquinas

Therefore he says Paul, — a name to be revered by all the faithful who have been taught by him — a prisoner. 2 Timothy 2:9: ‘in which I suffer even to bonds, as a criminal’. For now he is a prisoner in Rome, but of Christ Jesus, to give the reason for his chains. For it is highly praiseworthy to be imprisoned for the sake of Christ; for in this he is blessed. Matthew 5:10: ‘Blessed are they who suffer persecution for justice’ sake...’ 2 Peter 4:15: ‘Let none of you suffer as a murderer, or a thief, or a slanderer, or as one coveting what belongs to others. But if he suffers as a Christian, let him not be ashamed, but let him glorify God under this name.’ Acts 5.41: ‘So they departed from the Sanhedrin, rejoicing that they had been counted worthy to suffer disgrace for the name of Jesus.’
And our brother Timothy... They are brothers with regard to perfect faith. Philippians 2:20: ‘For I have no one so like-minded who is so genuinely solicitous for you.’ He joins Timothy to himself, that he might more easily succeed, because it is impossible that the prayers of many will not be heard.
Then he mentions the persons greeted. And first the principal person greeted, then others, particularly the husband and wife whose house it is, to whom the servant is obliged. To Philemon, our beloved and fellow worker, and to Appia, beloved sister... Beloved, he says on account of her good works. John 13:34: ‘This is my command, that you love one another.’ Fellow worker, because he ministers to the saints. Proverbs 18.19: ‘A brother that is helped by his brother is like a strong city.’ Then he mentions Archippus our fellow soldier, who was so powerful at Colossae that all Christians were under his protection.

‘If you have a faithful servant, let him be to you as your own soul’ (Sirach 33:31). The wise man shows three things concerning master and slave, namely, what is required on the side of the servant; what ought to be the feeling of the master towards the servant; and what is the use of the servant. From the servant fidelity is asked, for in this he is a good servant, because what he is and all that he has he ought to give to the master. Matthew 24-45: ‘Who, do you think, is the faithful and prudent servant...’ And he says, ‘if he is faithful’, because fidelity is found in few. Proverbs 20:6: ‘But who shall find a faithful man?’ The master ought to feel towards his servant as a friend, hence it is said, ‘as his own soul’. For this is proper to friends, that they are of one mind in what they will and what they do not will. Acts 4.32: ‘Now the multitude of the believers were of one heart and one soul.’ By which we are given to understand that there is a consensus of master and servant, when the faithful servant becomes a friend. As for his use, he should be treated like a brother, for he is a brother, both with respect to generation of nature, because they have the same author —Job 31.13: ‘If I have despised to abide judgement with my man-servant’; Malachi 2:10: ‘Have we not all one father? Did not one God created us?’ —and with respect to the generation of grace, which is the same for both. Galatians 3:27: ‘For all you who have been baptized into Christ, have put on Christ. There is neither Jew nor Greek; there is neither slave nor freeman; there is neither male nor female. For you are all one in Christ Jesus.’ Matthew 23:8: ‘And all you are brothers.’ These words are relevant to the matter of this epistle. For as it was shown above how spiritual prelates should relate to their subjects, so here he shows how temporal masters should relate to their temporal servants, and how the faithful servant to his master.
The occasion of the epistle is this. At Colossae an important Christian had a servant who secretly fled to Rome where he was baptized by the Apostle who now writes on his behalf. First he gives a greeting, followed by the narrative of the epistle. In the greeting he mentions persons who send their greeting and then the recipients and finally the good hoped for.