C. F. Keil and Franz Delitzsch on 1 Kings 15:6-8

1Ki 15:6-8 “And there was war between Rehoboam and Jeroboam all his life;” i.e., the state of hostility which had already existed between Rehoboam and Jeroboam continued “all the days of his life,” or so long as Abijam lived and reigned. If we take חיּיו כּל־ימי in this manner (not כּל־ימיהם, 1Ki 15:16), the statement loses the strangeness which it has at first sight, and harmonizes very well with that in 1Ki 15:7, that there was also war between Abijam and Jeroboam. Under Abijam it assumed the form of a serious war, in which Jeroboam sustained a great defeat (see 2 Chron 13:3-20). - The other notices concerning Abijam in 1Ki 15:7, 1Ki 15:8 are the same as in the case of Rehoboam in 1Ki 14:29, 1Ki 14:31.