John Wesley on 2 Chronicles 16:1

Of the reign - Or, of the kingdom of Asa, that is, of the kingdom of Judah, which was now Asa's kingdom; or from the time of the division of the two kingdoms. Rehoboam reigned seventeen years, Abijah three years, Asa had now reigned fifteen years, all which put together, make up the thirty five years mentioned chap.15:19, and in the next year Baasha wars against him; and the ground of the war was the defection of many of his subjects to Asa, chap.15:9.