ChristianAnswers.Net WebBible Encyclopedia
Symbolically, the heart is the center not only of spiritual activity, but of all the operations of human life. “Heart” and “soul” are often used interchangeably (Deut. 6:5; 26:16; compare Matt. 22:37; Mark 12:30-33), but this is not generally the case.
The heart is the “home of the personal life,” and hence a man is designated, according to his heart, wise (1 Kings 3:12, etc.), pure (Ps. 24:4; Matt. 5:8, etc.), upright and righteous (Gen. 20:5-6; Psalm 78:72), pious and good (Luke 8:15), etc. In these and such passages, the word “soul” could not be substituted for “heart.”
The heart is also the seat of the conscience (Rom. 2:15). It is naturally wicked (Gen. 8:21), and hence it contaminates the whole life and character (Matt. 12:34; 15:18; compare Eccl. 8:11; Ps. 73:7). Hence the heart must be changed, regenerated (Ezek. 36:26; 11:19; Ps. 51:10-14), before a man can willingly obey God.