Stand therefore, having your loins girt about with truth, and having on the breastplate of righteousness;
The second piece of the armour of God that Paul discusses in Ephesians 6 is the breastplate of righteousness. In the armour of a Roman soldier, the breastplate served as protection for some of the most important parts of the body.
Underneath the breastplate is the heart, lungs and other organs necessary for life. Therefore, if a soldier did not wear his breastplate, he was vulnerable to an attack that could result in instant death.
So, why does Paul call it the breastplate of righteousness? If we do not protect ourselves with righteousness, we open ourselves up to attack from the enemy and can fall into sin. To be righteous means to obey God’s commandments and live in a way that is honourable to Him.