The prophet warned that the natural human heart is deceitful above all things and oftentimes desperately wicked, originating evil thoughts and deeds within. [1] “The law written on hearts is a key aspect of the new covenant prophesied by Jeremiah and fulfilled in spiritual understanding.”. [2] “Let not your hearts be troubled, for I give you my peace and assure you of triumph through faith.”. [3] Ancients believed the soul resided in the heart, among various other body parts. [4]