9 and with [Tychicus], Onesimus, our faithful and beloved brother, who is one of you. They will tell you of everything that has taken place here.
10 Aristarchus my fellow prisoner greets you, and Mark the cousin of Barnabas (concerning whom you have received instructions—if he comes to you, welcome him), 11 and Jesus who is called Justus. These are the only men of the circumcision among my fellow workers for the kingdom of God, and they have been a comfort to me.
Who are these people with Paul?
Onesimus – (Philemon 8-22).
Onesimus was a runaway slave who became a believer in Jesus and connected with Paul. In his letter to Philemon, Paul explains that Onesimus had become useful to the gospel witness and he pleads with Philemon to take Onesimus back as a brother and not a servant. Paul calls Onesimus “faithful and beloved,” the very same descriptors of Tychicus. These brothers are entrusted to deliver the message of God to the Colossians.
Consider for a moment that a former slave who has been transformed by the gospel is delivering the message of Colossians. This letter is been focused on discovering the Christian’s new identity as it is in Christ. It is quite appropriate that a man who has had such a dramatic shift from slavery to freedom is responsible for delivering a message that speaks of a dramatic shift from slavery in sin to freedom in Christ. Onesimus is a living analogy for salvation.
Aristarchus (Acts 19:29, 20:4, 27:2, and Philemon 1:24)
A Macedonian believer, Aristarchus was one of Paul’s “companions in travel” (Acts 19:29). He was present at the riot in Ephesus and spent significant time with Paul in Ephesus. In the midst of extreme danger, Aristarchus remained faithful to stand by Paul. Further, exemplifying the Macedonian spirit, Aristarchus has given all of himself to the mission of God. He has sacrificed his own comfort and position by following the Lord even to prison. This man is a bold follower of Christ who stands by Paul in some of the most difficult circumstances. Even in this letter, he is a “fellow prisoner.” What a great encouragement to have brothers such as Aristarchus who will serve even in the most difficult of circumstances.
Mark (Acts 12:12, 12:25, 15:37-39, 2 Timothy 4:11, Philemon 24, 1 Peter 5:13)
John Mark, the cousin of Barnabas, was greatly involved in the ministry of the early church. He was a member of Paul’s missionary cohort early on, until he fell sick and had to return home. He and Barnabas worked to advance the Gospel apart from Paul for a time before they were evidently reunited at Paul’s request in 2 Timothy. Mark’s own journey was one of transformation. He went from being a nuisance to being a valuable part of the mission of God. In his first attempt to live on mission, he was overcome with sickness and then rejected by the leader of the mission. Yet, he persisted and grew as a disciple, faithfully proclaiming the gospel when given the opportunity. So, over time, he is transformed from the sickly and annoying boy that Paul does not want to bother with to being one whose presence is requested because he is “useful” (2 Tim. 4:11).
So it is with many Christians. As we grow in the Lord we often find the journey to becoming useful to be a long and rather slow process. Most Christians are more akin to John Mark than Paul. We seldom have a Damascus road experience that changes us overnight. Most of us must walk through failures and successes and learn slowly. Although we have been changed in a moment, we still must grow into that change as Mark grew.
Jesus called Justice (Only mentioned in Colossians.)
This brother was among the faithful cohort of Paul. We know little about him because he is only mentioned in this one verse of Colossians. We know that he is with Paul as he writes Colossians. We know that he was Jewish (that is what “among the circumcision” means). And we know that he was involved enough to deserve mention in the letter. Beyond that, we can only know Justus through his relationship to the others.
Identifying these men as “among the circumcision” draws the mind of the hearer to the hostile circumcision party that is mentioned throughout Acts. The church at Colossae would have been well aware of the adversarial nature of the Jews. They would have noticed how Paul was frequently followed by wealthy Jewish leaders who wanted to push the gospel message out of the cities of Asia Minor. In his identification of these brothers as “among the circumcision” Paul is sharing a victory with the church! The gospel has converted and transformed even those who were adversarial to it! The transforming power of the Gospel of Jesus Christ transcends all boundaries. Even the most antagonistic can be transformed to become an encouragement and a fellow worker in the Kingdom of God!
 There are some other “Justus” mentioned in Acts. They are not the same as the Justus mentioned here. Both the names Jesus and Justus were common names among Jewish people in the first century and as a result it is easy to conflate the various men with each other.