Contradiction with 1 Samuel 16:7
God looks on the heart, not outward appearances; not knowing contradicts this focus on internal understanding.
1 Samuel 16:7: But the LORD said unto Samuel, Look not on his countenance, or on the height of his stature; because I have refused him: for [the LORD seeth] not as man seeth; for man looketh on the outward appearance, but the LORD looketh on the heart. [outward...: Heb. eyes]
Contradiction with James 1:5
Encourages seeking wisdom from God, suggesting possible lack of understanding, which contradicts the implication of lacking understanding in Matthew 15:16.
James 1:5: If any of you lack wisdom, let him ask of God, that giveth to all [men] liberally, and upbraideth not; and it shall be given him.
Contradiction with Proverbs 4:7
Stresses the importance of acquiring wisdom, implying it's possible to lack understanding, contrary to the implication in Matthew 15:16.
Proverbs 4:7: Wisdom [is] the principal thing; [therefore] get wisdom: and with all thy getting get understanding.
Contradiction with 1 Corinthians 3:2
Suggests that some are not yet able to understand deeper teachings, contradicting the expectation in Matthew 15:16.
1 Corinthians 3:2: I have fed you with milk, and not with meat: for hitherto ye were not able [to bear it], neither yet now are ye able.