'Heart' in the Bible

but just as it is written,“Things which eye has not seen and ear has not heard,And which have not entered the heart of man,All that God has prepared for those who love Him.”

But he who stands firm in his heart, being under no constraint, but has authority over his own will, and has decided this in his own heart, to keep his own virgin daughter, he will do well.

the secrets of his heart are disclosed; and so he will fall on his face and worship God, declaring that God is certainly among you.