A good soldier would examine his breastplate to see that it was in good order. Christian soldiers should examine their righteousness to see if it is fit for use. While the imputed righteousness of Christ is always perfect and always fulfils its effects, the same cannot be said for the believer’s practical righteousness.
Therefore they need to look at the state of their breastplate and what use they are making of it. They are to ensure that there are no chinks in the armour through which the devil can fire an arrow. A lie is a chink, an angry word is a gap, a failure to fulfil one’s duty is a hole through which the devil’s arrows can come. Remember he is a speedy and accurate archer. There are many such chinks.
In a military battle, if a soldier’s breastplate was damaged, then he was in real danger because he had no means of fixing it. But in the Christian warfare, when a believer’s breastplate is damaged, he can immediately ask for the hole to be sorted by his general, who is not only the Commander of his people, but also their help. Amid the noise of the battle he hears the individual cry for help from one of his soldiers and immediately heals the gap that threatens to allow the devil through.
In putting on this breastplate they have the example of Jesus to follow. In Isaiah 59:17, which is a prophecy of the coming of the Saviour to help his people, the prophet predicts that the Messiah will ‘put on righteousness as a breastplate, and a helmet of salvation on his head’. Jesus loved righteousness and hated lawlessness throughout his life. When the devil tempted him, his love of obedience to God’s law was his protection against all the subtle suggestions of the enemy. Jesus is our example in this. He has left us an example to follow in his steps.