For out of the heart proceed evil thoughts, murders, adulteries, fornications, thefts, false witness, blasphemies

Matthew 15:18-20
But those things which proceed out of the mouth come from the heart, and they defile a 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, but to eat with unwashed hands does not defile a man.”

Our heart resides our innermost being where good and evil are present. Our Lord Yshua knows us well, and told us that the foul things coming from our mouth, are not just mere words. They have a presence rooted in our hearts. Knowing this, we can now examine the words coming out of our mouth and try to understand the source of the words. It is better that we examine and correct ourselves than God examining us.