And in the twentieth year of Jeroboam king of Israel reigned Asa over Judah. How this is to be accounted for See Gill on 1 Kings 15:2.

Reign of Asa (cf., 2 Chronicles 14-16). - As Asa ascended the throne in the twentieth year of the reign of Jeroboam, his father Abijam, who began to reign in the eighteenth year of Jeroboam (1 Kings 15:1), can only have reigned two years and a few months, and not three full years.

And in the twentieth year of Jeroboam king of Israel reigned Asa over Judah.

1Ki 15:9-22. Asa's Good Reign.

15:9-24 Asa did what was right in the eyes of the Lord. That is right indeed which is so in God's eyes. Asa's times were times of reformation. He removed that which was evil; there reformation begins, and a great deal he found to do. When Asa found idolatry in the court, he rooted it out thence. Reformation must begin at home. Asa honours and respects his mother; he loves her well, but he loves God better. Those that have power are happy when thus they have hearts to use it well. We must not only cease to do evil, but learn to do well; not only cast away the idols of our iniquity, but dedicate ourselves and our all to God's honour and glory. Asa was cordially devoted to the service of God, his sins not arising from presumption. But his league with Benhadad arose from unbelief. Even true believers find it hard, in times of urgent danger, to trust in the Lord with all their heart. Unbelief makes way for carnal policy, and thus for one sin after another. Unbelief has often led Christians to call in the help of the Lord's enemies in their contests with their brethren; and some who once shone brightly, have thus been covered with a dark cloud towards the end of their days.