Colossians 4:10
Aristarchus my fellowprisoner saluteth you, and Marcus, sister’s son to Barnabas, ( touching whom ye received commandments: if he come unto you, receive him;) Aristarchus my fellowprisoner saluteth you, and Marcus, sister’s son to Barnabas, ( touching whom ye received commandments: if he come unto you, receive him;)
Aristarchus is Paul's fellow prisoner, sharing his imprisonment and bondage by choice out of affection for him so that he could stay with him to help him and care for him in his hardships and afflictions, including during the voyage to Italy. Mark is Barnabas's nephew, his sister's son, and he was with Paul in Rome during his imprisonment among his companions and fellow workers who assisted and comforted him.
Mark had once deserted the mission and turned back from the work because he was discouraged by hardship, so Paul judged him unfit for ministry. Paul was afterward reconciled to Mark, their earlier disagreement being overcome, and he welcomed and received him as a fellow worker and fellow laborer. Paul commended and recommended Mark to the Colossians as a trusted fellow worker and trusted laborer, directing them to receive him if he came to them.
Mark thus became a fellow worker for God's kingdom and a personal comfort to Paul, devoting himself to proclaiming the gospel in difficult fields and later proving useful to Paul in ministry, showing that his earlier failure did not end his usefulness.