Jeremiah 17:9 in the King James Version
The heart is deceitful above all things, and desperately wicked: who can know it?
Context
8 For he will be as a tree planted by the waters, who spreads out its roots by the river, and will not fear when heat comes, but its leaf will be green, and will not be concerned in the year of drought. It won’t cease from yielding fruit.
9 The heart is deceitful above all things and it is exceedingly corrupt. Who can know it?
10 “I, the LORD, search the mind. I try the heart, even to give every man according to his ways, according to the fruit of his doings.”