The Armour of Light

Paul contrasts the gospel and evil metaphorically as light and darkness in Rom 13.12. He calls his readers to "cast off the works of darkness"—obviously speaking of evil and wickedness, indeed in the next verse he helpfully categorizes some (but not all) of what he means: rioting, drunkenness, chambering, wantonness, strife, envying—and to put on the armour of light (KJV). I find that reference interesting. Light (acting righteously) acts as our armor.

Armor is meant for protection so in some way acting righteously protects us. Obviously Paul does not mean that acting righteously saves us for that would contradict what he has already written. He must mean that acting righteously inoculates us from the grip of evil which lurks in every dark corner waiting to devour us, even in corners that appear benign. This is the nature of evil.