2 Chronicles 20:2 - Joseph Benson’s Commentary on the Old and New Testaments

Then there came some that told Jehoshaphat That brought him the surprising intelligence of this invasion, when his enemies had already entered his kingdom. Saying, There cometh a great multitude against thee from beyond the sea The Dead sea, beyond which mount Seir lay; and from this side Syria Largely so called, and so it includes the Moabites and Ammonites. And it may be thus expressed, to intimate that they came by the instigation of the Syrians, to revenge themselves of Jehoshaphat for joining with Ahab against them.