Matthew 12:34; Proverbs 4:23; Proverbs 10:11; Psalm 14:1; Proverbs 21:2; Proverbs 24:12; Ezekiel 11:21; Ezekiel 16:30; Luke 6:45

34 You brood of vipers! How can you speak good things, when you are evil? For out of the abundance of the heart the mouth speaks.
23 Keep your heart with all vigilance, for from it flow the springs of life.
11 The mouth of the righteous is a fountain of life, but the mouth of the wicked conceals violence.
1 Fools say in their hearts, "There is no God." They are corrupt, they do abominable deeds; there is no one who does good.
2 All deeds are right in the sight of the doer, but the Lord weighs the heart.
12 if you say, "Look, we did not know this"— does not he who weighs the heart perceive it? Does not he who keeps watch over your soul know it? And will he not repay all according to their deeds?
21 But as for those whose heart goes after their detestable things and their abominations, I will bring their deeds upon their own heads, says the Lord God.
30 How sick is your heart, says the Lord God, that you did all these things, the deeds of a brazen whore;
45 The good person out of the good treasure of the heart produces good, and the evil person out of evil treasure produces evil; for it is out of the abundance of the heart that the mouth speaks.