The Old Testament frequently uses "heart" (Heb. leb) to identify the source of a person"s thinking and acting. It describes the root of unconscious as well as conscious motivation. [source][source][source]
The human heart is deceptive; we may think we know why we do something, but really we may be doing it for another reason. It is naturally incurably sick, really totally depraved, and in need of healing. No one really understands his or her own corrupt heart, nor do we understand why our hearts behave as they do. [source][source][source]
"Unregenerate human nature is in a desperate condition without divine grace ..." [1][source]
Context Summary
Jeremiah 17:1-14 - Human And Divine Help Contrasted
The Jews were always seeking alliance either with Egypt or Babylon. What was true of them applies to us all; but we cannot depend upon human aid, without departing from the Lord. The heath is probably the juniper, a lonely tree, dwelling in arid wastes, unvisited by dew. The soul that rests on God is watered from His throne. The roots of such are fed from the hidden springs of Eternity. The heart is deceitful; it tends constantly to substitute the arm of flesh for the living God. Desperately wicked means "incurably sick." It was the ancient notion that the partridge stole the eggs of other birds and hatched them as her own. The covetous man is sure to reap disappointment. He steals other people's goods, but is driven off the nest before they hatch out for the benefit of himself. God's glorious throne is a defense to all who trust Him; while those who depart from Him shall be forgotten, as a sentence written in the sand is obliterated by the next puff of wind. Contrast Job 19:23-24. [source]
Chapter Summary: Jeremiah 17
1The captivity of Judah for her sin 5Trust in man is cursed; 7in God is blessed 9The deceitful heart cannot deceive God 12The salvation of God 15The prophet complains of the mockers of his prophecy 19He is sent to renew the covenant in hallowing the Sabbath
What do the individual words in Jeremiah 17:9 mean?
Deceitfulthe heartabove all [things]and desperately wickediswhocan know it