Jamieson, Fausset and Brown on Colossians 4:11

11. Justus--that is, righteous; a common name among the Jews; Hebrew, "tzadik" (Ac 1:23).

of the circumcision--This implies that Epaphras, Luke, and Demas (Col 4:12, 14) were not of the circumcision. This agrees with Luke's Gentile name (the same as Lucanus), and the Gentile aspect of his Gospel.

These only, &c.--namely, of the Jews. For the Jewish teachers were generally opposed to the apostle of the Gentiles (Php 1:15). Epaphras, &c., were also fellow laborers, but Gentiles.

unto--that is, in promoting the Gospel kingdom.

which have been--Greek, "which have been made," or "have become," that is, inasmuch as they have become a comfort to me. The Greek implies comfort in forensic dangers; a different Greek word expresses comfort in domestic affliction [Bengel].