for the sexually immoral, for homosexuals, for slave-traders, for liars, for perjurers, and for any other thing contrary to the sound doctrine;
Sound doctrine -- i.e. healthy (sounds like Dr. Luke influence on Paul here.) The participle of the Greek verb hygiaino (found also at 1 Timothy 6:3; 2 Timothy 1:13; 2 Timothy 4:3; Titus 1:9, Titus 1:13; Titus 2:1-2), here translated “sound,” includes the idea of “health” (in the sense of “healthy” or “health giving” doctrine), and in 2 Timothy it contributes to an extended metaphor in which false doctrine spreads poison insidiously through the body (“like gangrene,” 2 Timothy 2:17) while true doctrine makes the body healthy.