The Savior Himself is He Whom we are asked to put on. It is one and the same thing to say, 'Put on the whole armor of God,' and 'Put on the Lord Jesus Christ.' Our belt is truth and our breastplate is righteousness. The Savior is also called both 'truth' and 'righteousness.' On this principle He is also to be understood as the 'Gospel of peace.' He is Himself the 'shield of faith' and the helmet of salvation. He is the 'sword of the Spirit,' because He is the Word of God, living and efficacious, the utterance of which is stronger than any helmet and sharp on both sides.
-St. Jerome, Unknown, 5th century