This is a powerful statement on at least two levels:
1) Adherence to tradition has no purifying affect on us, and
2) Jesus, here, even more than in Acts 10, adjusts a major Old Covenant command (We are no longer held to Jewish dietary regulations).
New Covenant Christianity – the only type of real Christianity – always asks the question, “What really defiles me, causing all sorts of darkness to flow out of me?” It is never satisfied with merely fulfilling rules or standards. It always examines the heart.

Matthew 15:18