§ 02 · King James Bible
1 Kings 15:3
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.
Simple English
He did all the wrong things his father did and his heart didn't fully belong to the LORD like David's did.
* Work in progress - there may be occasional inaccuracies