What does the Bible say about the nature of the heart?

According to Jeremiah 17:9, the heart is described as deceitful above all things and desperately wicked. This means that the heart is inherently flawed, tainted by sin, and incapable of producing good in itself. The heart encompasses every aspect of a person, including thoughts, actions, motives, and intentions. Therefore, a new heart is required for true change, as expressed in Psalm 51 when David pleads, 'Create in me a clean heart, O God.' Without divine intervention, the fallen heart remains incurably polluted by sin.