Paul goes on to talk of the breastplate of righteousness. A Roman solider would have worn a breastplate made of bronze or chain mail which covered the vital organs (including the heart) and was fitted with loops or buckles that attached it to the belt. The breastplate of righteousness protects our hearts and emotions. It reminds us that God has given the righteousness of Christ to us (2 Cor 5:21) and therefore we don’t have to rely on our own righteousness (which in God’s sight is as filthy rags (Is 64:4)).
So often, the enemy tries to get us to rely on our own goodness or righteous acts, convincing us that we deserve favour because of how good we are. The truth is that apart from Christ, we can do nothing (John 15:5) and need to understand that we are now in Christ, so there is nothing left for us to do to earn God’s favour. In Christ, all the fulness of the Godhead dwells bodily and we have been given that same fulness in Him. (Col 2:9) When our hearts condemn us, Christ is greater than our hearts. (1 John 3:20). The breastplate of righteousness helps to protect our emotions as we put on the righteousness of Christ.