Albert Barnes Commentary 2 Chronicles 18:31

"And it came to pass, when the captains of the chariots saw Jehoshaphat, that they said, It is the king of Israel. Therefore they turned about to fight against him: but Jehoshaphat cried out, and Jehovah helped him; and God moved them [to depart] from him." — 2 Chronicles 18:31 (ASV)

And the Lord helped him ... - There is nothing corresponding to this passage in Kings. It is a pious reflection on the part of the author, who traces all deliverance to its real divine source.