Demas. This is the same person who afterwards forsook him, as he complains in the Second Epistle to Timothy (2-Timothy 4:10.) And if one of Paul's assistants, having become weary and discouraged, was afterwards drawn aside by the vanity of the world, let no man reckon too confidently on the zeal of a single year; but, considering how large a portion of the journey still remains to be accomplished, let him pray to God for steadfastness.

Marcus, Aristarchus, Demas, and Lucas - see the notes at the Epistle to the Colossians, Colossians 4:10, Colossians 4:14.

Marcus, Aristarchus, etc. - These were all acquaintances of Philemon, and probably Colossians; and may be all considered as joining here with St. Paul in his request for Onesimus. Some think that Marcus was either the evangelist, or John Mark, the nephew of Barnabas, Acts 12:12, Acts 12:25. Aristarchus was probably the same with him mentioned Acts 19:29; Acts 20:4; Acts 27:2. See Colossians 4:10.
Demas - Is supposed to be the same who continued in his attachment to Paul till his last imprisonment at Rome; after which he left him for what is supposed to have been the love of the world, but see the note on 2-Timothy 4:10.
Lucas - Is supposed to be Luke the evangelist, and author of the Acts of the Apostles. On these suppositions little confidence can be placed: they may be correct; they may be otherwise.

Marcus, Aristarchus, Demas, Lucas,.... Marcus was Barnabas's sister's son, the son of that Mary, in whose house the church met, and prayed for Peter when in prison; whose name was John Mark, whom Saul and Barnabas took along with them to Antioch, and from thence, in their travels, to other parts; but he leaving them at Pamphylia, was the occasion of a contention between Saul and Barnabas afterwards, when returned to Antioch; the latter insisting on his going with them again, and the former refusing it on account of his departure from them; which contention rose so high that they parted upon it, Acts 12:12 though after this the apostle was reconciled to him; he approving himself to be a faithful and useful minister of the Gospel; and therefore he desires Timothy to bring him along with him, 2-Timothy 4:11 and if this epistle was written after that, he was now come to him; however, he was now with him, whether before or after: Aristarchus was a Macedonian of Thessalonica; or very likely the apostle had been the instrument of converting him there, and who followed him from thence, and attended him wherever he went; he was with him in the uproar raised by Demetrius at Ephesus, and accompanied him into Asia; went with him in his voyage to Rome, and was now a fellow prisoner there, Acts 19:29. Demas is the same with him who is mentioned in 2-Timothy 4:10 and if this epistle is later than that, it should seem that he was restored from his fall, and was returned to the apostle. Lucas is the same with Luke the Evangelist, the beloved physician, the brother whose praise was in all the churches, and a constant companion of the apostle, in his travels; and who wrote the book called, "The Acts of the Apostles": these the apostle styles, "my fellow labourers", being all ministers of the Gospel; and this shows the apostle's great humility, so to call them, when they were far from being on an equal foot with him in office, gifts, or usefulness: and the Christian salutations of these persons are sent to Philemon, with this view, to engage him the more to attend to the apostle's request, in which they all joined.