Reign (basileuetō). Present active imperative, “let not sin continue to reign” as it did once (Rom 5:12).
Mortal (thnētoi). Verbal adjective from thnēskō, subject to death. The reign of sin is over with you. Self-indulgence is inconsistent with trust in the vicarious atonement.
That ye should obey (eis to hupakouein). With a view to obeying.