Matthew 12:35-37
The good man, out of the good treasure (heart) brings forth good things: and the wicked man out of the wicked treasure (heart) brings forth wicked things.
Hebrews 4:12-13
For the word of God is living, and powerful, and sharper than any two-edged sword, and piercing unto the dividing of soul and spirit, of both joints and marrow, and a quick discerner of the thoughts and intents of the heart.
James 1:26
But if any one seems to be religious, bridling not his own tongue, but deceiving his own heart, the religion of that man is vain.
James 3:2-10
For we all fail in many things; if any one fails not in word, the same is a perfect man, able even to bridle the whole body.