20. Brethren—an appellation calculated to conciliate their favorable reception of his exhortation.
children in understanding—as preference of gifts abused to nonedification would make you (compare 1Co 3:1; Mt 10:16; Ro 16:19; Eph 4:14). The Greek for "understanding" expresses the will of one's spirit, Ro 8:6 (it is not found elsewhere); as the "heart" is the will of the "soul." The same Greek is used for "minded" in Ro 8:6.
men—full-grown. Be childlike, not childish.