…and having put on the breastplate of righteousness
Why do we need the breastplate of righteousness? Isaiah 64:6 gives a very clear answer to this.
For all of us have become like one who is unclean, And all our righteous deeds are like a filthy garment; And all of us wither like a leaf, And our wrongdoings, like the wind, take us away
Righteousness is something we wear. Once that breastplate is on, the filthy rags of self-righteousness have vanished and we don the pure and righteous works of Jesus Christ.