'Hearts' in the Bible

Do not harden your hearts as [your fathers did] in the rebellion [of Israel at Meribah],On the day of testing in the wilderness,

“Therefore I was angered with this generation,And I said, ‘They always go astray in their heart,And they did not know My ways [nor become progressively better and more intimately acquainted with them]’;

while it is said,“Today [while there is still opportunity] if you hear His voice,Do not harden your heart, as when they provoked Me [in the rebellion in the desert at Meribah].”

He again sets a definite day, [a new] “Today,” [providing another opportunity to enter that rest by] saying through David after so long a time, just as has been said before [in the words already quoted],“Today if you hear His voice,Do not harden your hearts.”

“For this is the covenant that I will make with the house of IsraelAfter those days, says the Lord:I will imprint My laws upon their minds [even upon their innermost thoughts and understanding],And engrave them upon their hearts [effecting their regeneration].And I will be their God,And they shall be My people.

“This is the covenant that I will make with themAfter those days, says the Lord:I will imprint My laws upon their heart,And on their mind I will inscribe them [producing an inward change],”He then says,

let us approach [God] with a true and sincere heart in unqualified assurance of faith, having had our hearts sprinkled clean from an evil conscience and our bodies washed with pure water.