Luke 6:45 (ESV)
45 The good person out of the good treasure of his heart produces good, and the evil person out of his evil treasure produces evil, for out of the abundance of the heart his mouth speaks.
Psalm 119:11 (ESV)
11 I have stored up your word in my heart, that I might not sin against you.
Proverbs 4:23 (ESV)
23 Keep your heart with all vigilance, for from it flow the springs of life.