Mark 7:21-22
For it is from inside, from men's hearts, that designs of evil come; immorality, stealing, murder, adultery,
Luke 6:45
A good man, out of the good he has accumulated in his heart, produces good, and a bad man, out of what he has accumulated that is bad, produces what is bad. For his mouth says only what his heart is full of.
James 1:26
If anyone thinks he is religious, and does not bridle his tongue, but deceives himself, his religious observances are of no account.
James 3:5-8
So the tongue is a little organ and yet very boastful. What a great forest a spark will set on fire!