'Heart' in the Bible

Because, knowing God, they didn't glorify him as God, neither gave thanks, but became vain in their reasoning, and their senseless heart was darkened.

But according to your hardness and unrepentant heart you are treasuring up for yourself wrath in the day of wrath, revelation, and of the righteous judgment of God;

but he is a Jew who is one inwardly, and circumcision is that of the heart, in the spirit not in the letter; whose praise is not from men, but from God.

But thanks be to God, that, whereas you were bondservants of sin, you became obedient from the heart to that form of teaching whereunto you were delivered.

that I have great sorrow and unceasing pain in my heart.

But the righteousness which is of faith says this, "Don't say in your heart, 'Who will ascend into heaven?' (that is, to bring Christ down);

But what does it say? "The word is near you, in your mouth, and in your heart;" that is, the word of faith, which we preach:

that if you will confess with your mouth that Jesus is Lord, and believe in your heart that God raised him from the dead, you will be saved.

For with the heart, one believes unto righteousness; and with the mouth confession is made unto salvation.