SALUTATION. James, a servant of God and of the Lord Jesus Christ. (On the person who thus describes himself, see the Introduction) It is noteworthy that he keeps entirely out of sight his natural relationship to our Lord, and styles himself simply "a bond-servant of God and the Lord Jesus Christ."
That, and that alone, gave him a right to speak and a claim to be heard. δοῦλος is similarly used by St. Paul in Romans 1:1; Philippians 1:1; Titus 1:1 by St. Peter in 2 Peter 1:1; and by St. Jude Jude 1:1.
It is clearly an official designation, implying that his office is one "in which, not his own will, not the will of other men, but only of God and of Christ, is to be performed" (Huther). To the twelve tribes, etc.
Compare the salutation in Acts 15:23, which was also probably written by St. James: "The apostles and the elder brethren unto the brethren which are of the Gentiles in Antioch, and Syria, and Cilicia, greeting."