Hebrews 4:12 For the word of God is quick, and powerful, and sharper than any twoedged sword, piercing even to the dividing asunder of soul and spirit, and of the joints and marrow, and is a discerner of the thoughts and intents of the heart.
Heart: Kardia; "Stands for man’s entire mental and moral activity The heart is used figuratively for the hidden springs of personal life. It is the thoughts or feelings, mind, the middle. Fleshly tables of the heart (the eyes of our understanding). It is the mind, will, emotions, thoughts, feelings, reasons, and intentions.'
We believe with our heart the middle part, or core of our soul. It is the hiding place of our spirit.
Proverbs 4:23 (Amplified) “ Keep and guard your heart with all vigilance and above all that you guard, for out of it flow the springs of life.”