All of the following verses reference King David’s heart.

For it came to pass, when Solomon was old, that his wives turned away his heart after other gods: and his heart was not perfect with the Lord his God, as was the heart of David his father. I Kings 11:4 (KJV) emphasis mine

And rent the kingdom away from the house of David, and gave it thee: and yet thou hast not been as my servant David, who kept my commandments, and who followed me with all his heart, to do that only which was right in mine eyes. I Kings 14:8 (KJV) emphasis mine

And he walked in all the sins of his father, which he had done before him: and his heart was not perfect with the Lord his God, as the heart of David his father. I Kings 15:3 (KJV) emphasis mine

According to God, David had a perfect heart- not in the sense that he never sinned or failed God- but in its sincerity. We can read his life story and easily see that he had weakness in his flesh and made bad decisions, disobeying God and His Word. Therefore, if he had all these issues and more, how could his heart be considered perfect or right before God? How could God look at David and say that David did only what was right in His eyes when clearly he did not?

God considered (and still considers) David’s heart perfect because David never turned away from the Lord. He never stopped worshiping and serving Him. When he was made aware of sin, he quickly confessed and repented. He continued to live for God and love God. David wasn’t considerecd perfect in his heart because of performance, but because he loved God. The key is that God sees our hearts, but man sees our actions. God looks at our “who,” and man looks at our “do.”

Sin is never right in God’s eyes, but our spirit is willing while our flesh is weak. God separates our who (His children who love Him and want to please Him) from our do. Yes, we deal with flesh and with the enemy- and we sometimes give in to them. But, if we keep our hearts fixed on God, God will bring us through . And if we continue to seek Him and love Him in the process, He will say of each of us: “You are a person after My own heart. You try to do my will.” God will see us as He did David, with a perfect, sincere heart.