'Hearts' in the Bible

that their hearts may be comforted, they being knit together in love, and unto all riches of the full assurance of understanding, that they may know the mystery of God, even Christ,

And let the peace of Christ rule in your hearts, to the which also ye were called in one body; and be ye thankful.

Let the word of Christ dwell in you richly; in all wisdom teaching and admonishing one another with psalms and hymns and'spiritual songs, singing with grace in your hearts unto God.

whom I have sent you for this very purpose, that ye may know our state, and that he may comfort your hearts;