George Leo Haydock

Let not sin, therefore, reign, &c. He compares sin and justice to two kings, or generals, under one of which every man fights in this world. Sin is the tyrant, under which fight the wicked, and make their minds and their members the instruments, or arms of iniquity to sin, when they follow and yield to their disorderly lusts. But he exhorts them to live so as to make the powers of their souls, and their members, instruments or arms of justice to God, to fight under God, their lawful king, and under the banner of his justice. (Witham)