(Psalms 26:2) - Examine me, O Lord, and prove me; try my reins and my heart.

The heart is said to be the center of our emotions. If our heart dies, our whole body dies. The amygdala, where those emotions are processed, is the place where what we think leaves our mouths and is spoken one to another, whether good or bad. Just as the kidney is the most vulnerable part of the body, the heart is also.

David asks the Lord to examine him, test him, and see what is in his heart and mind. David says, Search me, O God, and know my heart: try me, and know my thoughts: And see if there be any wicked way in me, and lead me in the way everlasting. (Psalms 139:23-24)

Out of the abundance of the heart, the mouth speaks. What is our mouth saying? (Matthew 12:34)

The mind is where God meets us and has a little talk with us. The mind is where all of our thoughts come to fruition. I, the Lord, search the heart and test the mind to give every man every man according to his ways, according to the fruit of his deeds. (Jeremiah 17:10)