Contradiction with Jeremiah 17:9
Contradicts by stating the heart is deceitful and desperately wicked, unlike Proverbs 23:15, which suggests a heart that is wise.
Jeremiah 17:9: The heart [is] deceitful above all [things], and desperately wicked: who can know it?
Contradiction with Genesis 8:21
Contrasts by implying human hearts are inherently inclined to evil from youth, differing from the goodness assumed in Proverbs 23:15.
Genesis 8:21: And the LORD smelled a sweet savour; and the LORD said in his heart, I will not again curse the ground any more for man's sake; for the imagination of man's heart [is] evil from his youth; neither will I again smite any more every thing living, as I have done. [a sweet...: Heb. a savour of rest or, satisfaction] [for the imagination: or, through the imagination]
Contradiction with Ecclesiastes 9:3
Describes the heart of humans as full of evil and madness, opposing the wise heart mentioned in Proverbs 23:15.
Ecclesiastes 9:3: This [is] an evil among all [things] that are done under the sun, that [there is] one event unto all: yea, also the heart of the sons of men is full of evil, and madness [is] in their heart while they live, and after that [they go] to the dead.