Contradiction with James 3:10
This verse reveals that both blessing and cursing can come from the same mouth, contradicting Proverbs 4:24's call for only purity from one's speech.
James 3:10: Out of the same mouth proceedeth blessing and cursing. My brethren, these things ought not so to be.
Contradiction with Matthew 15:11
This verse suggests that it is not what enters the mouth that defiles a person, implying that speech alone is not the determinant of purity, which contradicts the focus in Proverbs 4:24 on pure speech.
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 Ecclesiastes 7:21
This verse advises not to take to heart everything people say, acknowledging the presence of perverse speech, thus contrasting with the proactive elimination of such speech in Proverbs 4:24.
Ecclesiastes 7:21: Also take no heed unto all words that are spoken; lest thou hear thy servant curse thee: [take...: Heb. give not thine heart]
Contradiction with Job 2:10
Job acknowledges speaking "foolishly" when facing adversity, showing that even the righteous may falter in speech, which contrasts with the ideal of maintaining pure speech in Proverbs 4:24.
Job 2:10: But he said unto her, Thou speakest as one of the foolish women speaketh. What? shall we receive good at the hand of God, and shall we not receive evil? In all this did not Job sin with his lips.