Interestingly enough, Paul writes in Romans 10:10 10 With the heart one believes, resulting in righteousness, and with the mouth one confesses, resulting in salvation.
With the heart one believes. How can that be?
Genesis 6:5 - Then the LORD saw that the wickedness of man was great on the earth, and that every intent of the thoughts of his heart was only evil continually.
Genesis 8:21 -The LORD smelled the soothing aroma; and the LORD said to Himself, "I will never again curse the ground on account of man, for the intent of man's heart is evil from his youth; and I will never again destroy every living thing, as I have done.
Psalm 14:1 -The fool has said in his heart, "There is no God." They are corrupt, they have committed abominable deeds; There is no one who does good. (Emphasis Mine)
Jeremiah 17:9 -"The heart is more deceitful than all else And is desperately sick; Who can understand it?
The heart is the most wicked thing we have (ok..not the physical one that pumps blood--I think we all know that!) How can one believe in God with a wicked, rotten heart? Only if God gives a new heart. Then, and only then, can someone believe.