the breastplate of righteousness: A breastplate is a piece of armor that covers the chest to protect the heart and other vital organs during battle. In the Bible, Paul uses this image to show how righteousness—being right with God and living in a right way—protects a believer’s heart and life from the attacks of the devil. This righteousness is either:
the righteousness God gives to those who believe in Christ, or
the righteous way of life that the Spirit of God creates in believers.
Each one suggests the presence of the other.