Heart in Scripture is used in various ways. Sometimes it means our reason or understanding, sometimes our affections and emotion, and sometimes our will. Generally it denotes the whole soul of man and all its faculties, not individually, but as they all work together in doing good or evil. The mind as it reasons, discerns, and judges; the emotions as they like or dislike; the conscience as it determines and warns; and the will as it chooses or refuses – are all together called the heart.
Jerry Bridges