See on v. 19. He who is a “slave” of God brings forth permanent and highly desirable fruit, namely, the fruit of the Spirit (Gal. 5:22). Such service means the development of all the powers of mind, body, and soul (Rom. 12:1, 2), and results in eternal life (see chs. 2:7; 5:21).
Become servants.
Or, “become enslaved.” The same Greek word being used as in v. 18 (see comment there). Paul was not ashamed to call himself the slave of Christ (see on ch. 1:1). However, in our service to God we do not obey Him because we are under bondage, but because we love Him (John 14:15), and God in turn does not actually treat us as slaves but as sons (Gal. 4:7).