'Heart' in the Bible

Grace to you and peace [inner calm and spiritual well-being] from God our Father and the Lord Jesus Christ.

but just as it is written [in Scripture],“Things which the eye has not seen and the ear has not heard,And which have not entered the heart of man,All that God has prepared for those who love Him [who hold Him in affectionate reverence, who obey Him, and who gratefully recognize the benefits that He has bestowed].”

But the natural [unbelieving] man does not accept the things [the teachings and revelations] of the Spirit of God, for they are foolishness [absurd and illogical] to him; and he is incapable of understanding them, because they are spiritually discerned and appreciated, [and he is unqualified to judge spiritual matters].

For who has known the mind and purposes of the Lord, so as to instruct Him? But we have the mind of Christ [to be guided by His thoughts and purposes].

But the man who stands firmly committed in his heart, having no compulsion [to yield to his daughter’s request], and has authority over his own will, and has decided in his own heart to keep his own virgin [daughter from being married], he will do well.

the secrets of his heart are laid bare. And so, falling on his face, he will worship God, declaring that God is really among you.