Contradiction with Matthew 15:11
It focuses on what comes out of the mouth, not just the heart, as what defiles a person, similar to Mark 7:20 but emphasizes words.
Matthew 15:11: Not that which goeth into the mouth defileth a man; but that which cometh out of the mouth, this defileth a man.
Contradiction with James 1:26
Implies that controlling one's speech is crucial to being religious, suggesting that external actions also matter.
James 1:26: If any man among you seem to be religious, and bridleth not his tongue, but deceiveth his own heart, this man's religion [is] vain.
Contradiction with Romans 14:14
States that nothing is unclean in itself, indicating that external things can be clean, differing from the idea in Mark 7:20.
Romans 14:14: I know, and am persuaded by the Lord Jesus, that [there is] nothing unclean of itself: but to him that esteemeth any thing to be unclean, to him [it is] unclean. [unclean: Gr. common]