10 And he called the multitude, and said unto them, Hear, and understand: 11 Not that which goeth into the mouth defileth a man; but that which cometh out of the mouth, this defileth a man. (Matthew 15:10-11 KJV)
William Burkitt’s Commentary
Our blessed Saviour leaving the Pharisees with some dislike, applies himself to the multitude, and shews them the true spring and original fountain of all spiritual pollution and uncleanness; namely, the filthiness and impurity of man’s heart and nature, which boiling in the heart, the scum runs out at the mouth: thereby informing the multitude, that not that which is eaten, but that which is spoken, defiles a man: not the meat eaten with the mouth, but the wickedness of the heart vented by the mouth, pollutes a person in God’s account.