A.T. Robertson Commentary Romans 6:12

"Let not sin therefore reign in your mortal body, that ye should obey the lusts thereof:" — Romans 6:12 (ASV)

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