My son, give attention to my words; Incline your ear to my sayings. Do not let them depart from your eyes; Keep them in the midst of your heart; For they are life to those who find them, and health to all their flesh. Keep your heart with all diligence, for out of it spring the issues of life. Proverbs 4:20-23

But those things which proceed out of the mouth come from the heart, and they defile a man. For out of the heart proceed evil thoughts, murders, adulteries, fornications, thefts, false witness, blasphemies. Matthew 15:18–19