Abijam's short reign showed the drift of Judah, yet God kept a lamp burning in Jerusalem for David's sake. The phrase points to God's covenant with David (2 Samuel 7). The narrator honestly notes David's one great failure, the matter of Uriah, while still holding him up as the model of a heart wholly devoted to God.
Asa brought reform. He removed idols, put away shrine practices, and removed his grandmother Maacah from her honored position because she had made an Asherah image. He cut it down and burned it at the Kidron. This shows that loyalty to God came before family rank. The high places remained, but Asa's heart was perfect with Yahweh all his days.
Asa's response to Baasha's pressure was less admirable. He took temple treasure and bought an alliance with Ben Hadad of Syria. Second Chronicles 16 records that a prophet rebuked him for relying on Syria rather than on God. In Israel, Baasha took the throne from Nadab and struck down Jeroboam's whole house, fulfilling Ahijah's word. Yet Baasha repeated Jeroboam's sin. Judgment that falls on others does not make us righteous. In the New Testament, Paul says that the one who judges others but does the same things condemns himself (Romans 2:1).