Matthew 15:19.

“Out of the heart come evil thoughts.”

The teachers of the Law could hardly believe that Jesus allowed his disciples to contaminate themselves by eating without the ritualized washing. They were convinced that contamination entered the person who eats with ritually unwashed hands.

Matthew was astounded how Jesus’ view of personal holiness was diametrically opposed to the prevailing Jewish teaching. Jesus flipped the whole argument by insisting that it is not what a person puts in his or her mouth that contaminates the person but what comes out of the mouth.

Matthew asks us to listen carefully as he quotes the words of Jesus.  Listen and understand, “What goes into a man’s mouth does not make him ‘unclean’ but what comes out of his mouth, that is what makes him ‘unclean.'” v 10

Jesus went on to explain. “The things that come out of the mouth come from the heart, and these make a man ‘unclean.'” The issue is the heart, not the mouth. An unclean “heart” can not be cleansed by mere washing the hands. Whether you wash or not makes absolutely no difference. The unclean heart remains unclean. And uncleanness can not produce cleanless.

So Jesus insist that the heart must be cleansed.