The Bible records that David, the shepherd boy chose not to wear the armor of a soldier, that King Saul armed him with, when he averred to fight the giant, Goliath (1 Samuel 17:38-39). But David did wear another kind of armor, an armor that was more effective than the physical armor that he chose not to wear, against an armored foe. It was a spiritual armor that He wore.
A breastplate guards for the most part the main and important organs in a human body. One of the vital organs is the heart. When the heart stops beating, one no longer lives. David was known to be a man after God’s own heart. In other words, he guarded his heart so that his life was one that was pleasing to God. The Bible tells us that out of the heart comes the issues (wellspring) of life (Proverbs 4:23) and at the same time, out of it comes the things that defile a man (Matthew 15:19-20). At the time of the battle with Goliath, David wore the breastplate of righteousness, standing strong with an emboldened heart that did not fail in fear, for He trusted in the One called The RIGHTEOUS (Jeremiah 23:6). The Lord is my Righteousness (Romans 3:22).
We must also recognize that the man whose heart was after God’s own heart, at a later stage in his life, lets his guard down, when he lets his heart wander away from God. In other words, the moment when David took off his breastplate of righteousness as he saw Bathsheba, he faltered and fell into the sin of adultery and murder. Like Samson, the man who fought the lion in the fields, now could not fight the lust within, because he took off the guard (breastplate) over his heart. He let his heart to be wounded as he grieved over the life of his son, and even worse as he felt that the joy of God’s Salvation could be taken from him (Psalm 51:12).
Let us be fervent in our prayers to be always armed with the breastplate of Righteousness, lest we let our hearts to be pierced.
Proverbs 4:23 (KJV)
23 Keep thy heart with all diligence; for out of it are the issues of life.