What comes out of your mouth, Jesus said, reveals your heart/life.
16 And Jesus said, Are ye also yet without understanding?
17 Do not ye yet understand, that whatsoever entereth in at the mouth goeth into the belly, and is cast out into the draught?
18 But those things which proceed out of the mouth come forth from the heart; and they defile the man.
19 For out of the heart proceed evil thoughts, murders, adulteries, fornications, thefts, false witness, blasphemies:
20 These are the things which defile a man: Mt 15:15–20.
34 O generation of vipers, how can ye, being evil, speak good things? for out of the abundance of the heart the mouth speaketh.
35 A good man out of the good treasure of the heart bringeth forth good things: and an evil man out of the evil treasure bringeth forth evil things.
36 But I say unto you, That every idle word that men shall speak, they shall give account thereof in the day of judgment.
37 For by thy words thou shalt be justified, and by thy words thou shalt be condemned. Mt 12:34–37.
4 Beloved, believe not every spirit, but try the spirits whether they are of God: because many false prophets are gone out into the world. 1 Jn 4.
12 For the word of God is quick, and powerful, and sharper than any twoedged sword, piercing even to the dividing asunder of soul and spirit, and of the joints and marrow, and is a discerner of the thoughts and intents of the heart. 13 Neither is there any creature that is not manifest in his sight: but all things are naked and opened unto the eyes of him with whom we have to do. Heb 4:12–13.