The tongue is a very good barometer of the heart. Jesus, after dealing with the Pharisees who accused him of casting demons out by the power of demons, says to them in Matthew 12:34–37,
Joseph A. PipaYou brood of vipers! How can you, being evil, speak what is good? For the mouth speaks out of that which fills the heart. The good man out of his good treasure brings forth what is good and the evil man out of his evil treasure brings forth what is evil. I say to you that every callous word that man shall speak, they shall render account for it in the day of judgment. For by your words you shall be justified and by your words you shall be condemned.Christ is showing here that, because of that close relationship of word to heart, our words will be the demonstration of the condition of our heart.1
26 If anyone thinks he is religious and does not bridle his tongue but deceives his heart, this person’s religion is worthless.