In Jeremiah, chapter seventeen, verse nine, “The heart is deceitful above all things, and desperately wicked: who can know it?” The heart is the inner being of a person that includes one’s desires, feelings, and thoughts. Above all, it is desperately evil and corrupt; as a result, people turn to selfishness and evil rather than God’s way of righteousness. The corrupt human heart is beyond cure and cannot be changed on its own. The only remedy is to experience God’s grace, be born again through faith in Christ, and receive a new heart – one that hates evil and delights in doing God’s will.
The heart, the conscience of a person, calls evil good and good evil, and cries peace to those to whom it does not belong. Herein, the heart is desperately wicked; it is deadly, it is desperate. For example, if the conscience, which should set right the errors of other faculties, is a leader in the delusion. We cannot know our hearts, nor what they will do in an hour of temptation. Who can understand their errors? Can we know the hearts of others, or depend upon them?
The people who believe God’s testimony in this matter and learn to watch their own hearts will find this a correct, though a sad picture, and learn many lessons to direct their conduct. But much in our own hearts and in the hearts of others will remain unknown. Yet whatever wickedness is in the heart, God sees it. Individuals may encounter something unpleasant or be compelled to behave a certain way, but God cannot be deceived.
A heart deceitful and desperately wicked: who can know it? Nobody, only the Lord Jesus Christ, who bore all of our sins while we were born in it, as in Psalm fifty-one, verse five.