Offering and understanding the Biblical word heart, and its deepest and truest meaning is a really good place to start. The subject of “Heart” in scripture is indeed both deep and broad. Obviously, there are going to be some passages that refer to the physical heart; the actual blood-pumping organ in our chest, but the most often used definition/description can be summarized by Easton’s Illustrated Dictionary of Biblical Terms.
Regarding the heart , Easton’s declares,
The heart is that center of spiritual activity and all the operations of human life.3