But those things which proceed out of the mouth come from the heart, and they defile a man.
Matthew 15:18
Surrounding context
15:17 Do you not yet understand that whatever enters the mouth goes into the stomach and is eliminated?
15:18 But those things which proceed out of the mouth come from the heart, and they defile a man.
15:19 For out of the heart proceed evil thoughts, murders, adulteries, fornications, thefts, false witness, blasphemies.