Jeremiah 17:9, "The heart is deceitful above all things, and desperately sick; who can understand it?"
Whenever we read the bible, we must keep context in mind. In chapter 17, Jeremiah is discussing Judah's sin and deserved punishment. In verse 9, the Lord is quoted as saying the above verse. In verse 10, God goes on to say, "I, the Lord, search the heart, I test the mind, even to give every man according to his ways, according to the fruit of his doings."
Although the direct context is Judah's sin, the statement that God makes in 17:9 is a general one that appears to apply to much more than just Judah. Considering that God in verse 10 speaks of "every man," it seems clear that Jeremiah 17:9 is an accurate descriptor of the hearts of all individuals prior to salvation.
What are we to make of this? What is the significance of Jeremiah 17:9?
I think we can come to a few conclusions. First, since the heart is designed to describe the most important parts of a man, we can conclude that man is completely deceitful and wicked. There are no parts of him that are good. Second, it is safe to say that all people are sinful. Third, it is clear that all people are guilty before God. Fourth, all people need a Savior because they deserve God's righteous wrath.
Jeremiah 17:9 accurately shows us the state of man before salvation. He is deceitful and wicked. The verse is very helpful because it shows that there is no room for pride in this world. We are all equally guilty before a holy judge. We all need to be saved, but because we are wicked we cannot save ourselves. We need someone righteous to save us.