Albert Barnes on Matthew 15:10-14

See also Mk 7:15-17. And he called the multitude. In opposition to the doctrines of the Pharisees, the Saviour took occasion to show them that the great source of pollution was the heart. They supposed that external things chiefly defiled a man. On this all their doctrines about purification were founded. This opinion of the Jews it was of great importance to correct, he took occasion, therefore, to direct the people to the true source of defilement--their own hearts. He particularly directed them to it as of importance:--Hear and understand!