[Jer 17:9 KJV] 9 The heart [is] deceitful above all [things], and desperately wicked: who can know it?
Background is needed for that passage.
Jeremiah 17:1-4
“Judah’s sin is engraved with an iron tool,
inscribed with a flint point,
on the tablets of their hearts
and on the horns of their altars.
Even their children remember
their altars and Asherah poles
beside the spreading trees
and on the high hills.
My mountain in the land
and your wealth and all your treasures
I will give away as plunder,
together with your high places,
because of sin throughout your country.
Through your own fault you will lose
the inheritance I gave you.
I will enslave you to your enemies
in a land you do not know,
for you have kindled my anger,
and it will burn forever.”
Jeremiah had been preaching against the murderous phallic cult practices that his people were saturating themselves with.
As revealed in other passages... His ex-fiance even joined them.
It tore him up! She kept coming around to taunt Jeremiah.
Jeremiah was painfully heartbroken!
God's words to Jeremiah was about her actions and his degenerate people was to tell Jeremiah that they had become a deceitful heart. Beyond knowing!
Warning Jeremiah that he will be baffled/tormented by how they could become that way.
God was telling Jeremiah that what they had become can not be understood (who can know it?)
It is not simply... the heart is deceitful, as if it applies universally.
But, rather,
"The deceitful heart is above all things desperately wicked and beyond finding out."
It was commentary as to how sin and evil will distort the souls of men you used to know beyond being able to know them anymore.
Its amazing how passages gets universally abused to mean all men have a deceitful heart.
John 1:47
Jesus saw Nathanael coming toward Him, and said of him,
“Behold, an Israelite indeed, in whom is no deceit!”
.