Every one that committeth sin is the bondservant of sin (pa o poiwn thn amartian doulo estin [th amartia]). The Western class omits th amartia (sin), but that is the idea anyhow. Note the use of poiwn (present active participle, continuous habit or practice), not poihsa (aorist active participle for single act), precisely as in 1 John 3:4-8 . Note also 1 John 3:21 for o poiwn thn alhqeian (the one who practises the truth). Sin, like the worst narcotic, is habit forming. Hence the problem today for criminologists for paroled or pardoned criminals nearly always go back to crime, sink again into sin, the slaves of sin. Xenophon has this notion of the slavery of sin (Memor. IV. 5. 3). So Paul clearly in Romans 6:17Romans 6:20 "slaves of sin" (douloi th amartia).