'Heart' in the Bible

But just as it is written, "[Things] which eye has not seen and ear has not heard, and have not entered into the heart of man, all that God has prepared for those who love him."

But he who stands firm in his heart, not having necessity, but has authority concerning his own will, and has decided this in his own heart, to keep his own virgin, he will do well.

the secret things of his heart become evident, and so, falling on [his] face, he will worship God, proclaiming, "God is truly among you!"