'With All Your Heart' in the Bible

Then Samuel said to all the house of Israel, “If you are returning to the Lord with all your heart, remove the foreign gods and the Ashtaroth (pagan goddesses) from among you and direct your hearts to the Lord and serve Him only; and He will rescue you from the hand of the Philistines.”

Samuel said to the people, “Do not be afraid. You have [indeed] done all this evil; yet do not turn away from following the Lord, but serve the Lord with all your heart.

Only fear the Lord [with awe and profound reverence] and serve Him faithfully with all your heart; for consider what great things He has done for you.