Gr. doulos, “slave” (see on John 8:34; Rom. 1:1). Paul here refers especially to the Christian minister.
Must not strive.
Or, “must not quarrel” (see on v. 23). The minister’s time is too valuable to be wasted on “foolish and unlearned questions” (v. 23). Furthermore, he should exhibit a worthy example before his church members by stressing the essential business of Christianity, which is character development.