'With All Your Heart' in the Bible

And Samuel spake unto all the house of Israel, saying, If ye do return unto the LORD with all your hearts, then put away the strange gods and Ashtaroth from among you, and prepare your hearts unto the LORD, and serve him only: and he will deliver you out of the hand of the Philistines.

And Samuel said unto the people, Fear not: ye have done all this wickedness: yet turn not aside from following the LORD, but serve the LORD with all your heart;

Only fear the LORD, and serve him in truth with all your heart: for consider how great things he hath done for you.