Reign (βασιλευετω). Present active imperative, "let not sin continue to reign" as it did once (Romans 5:12).

Mortal (θνητο). Verbal adjective from θνησκω, 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 (εις το υπακουειν). With a view to obeying.