1 Kings 15:19

There is a league between me and thee, and between my father and thy father; whereby it appears, that albeit he was an adversary to Israel all Solomon's days, 1 Kings 11:25, yet after the division of the kingdoms of Israel and Judah he was in league with both of them; either because his designs lay upon the enlargement of his empire other ways; or rather, because he thought it his wisdom and interest to leave them to themselves, to undo one another by their intestine wars, and so to prepare the way to his conquest of both; whereas his invading of either of them might have made up the breach, and forced them to unite against their common enemy. And therefore as soon as he was free from this fear, and one of them needed and earnestly desired his help against the other, he gladly embraced the opportunity. That he may depart from me; that being called to defend himself, he may be forced to depart from my territories.