Albert Barnes Commentary 1 Kings 15:18

"Then Asa took all the silver and the gold that were left in the treasures of the house of Jehovah, and the treasures of the king`s house, and delivered them into the hand of his servants; and king Asa sent them to Ben-hadad, the son of Tabrimmon, the son of Hezion, king of Syria, that dwelt at Damascus, saying," — 1 Kings 15:18 (ASV)

Left - Or, according to another reading, “found.” The wealthy condition of the temple treasury is sufficiently indicated in 1 Kings 15:15. (Compare to 2 Chronicles 15:18).

Asa’s conduct in calling Benhadad to his aid, condemned by the seer Hanani (2 Chronicles 16:7), cannot, of course, be justified, but there was much to excuse it. An alliance, it appears, had existed between Abijam and Tabrimon, Benhadad’s father (1 Kings 15:19)—an alliance which may have helped Abijam to gain his great victory over Jeroboam and achieve his subsequent conquests (2 Chronicles 13:17–20). This had been brought to an end by Baasha, who had succeeded in inducing Benhadad to enter into a league with him.

It was only natural that Asa should endeavor to break up this league. Politically speaking, he had a full right to go further and obtain, if he could, the support of the Syrian troops for himself. The Israelites had set the example of calling in a foreign power when Jeroboam obtained the aid of Shishak.

To Benhadad - For the probable succession of the Damascene kings and the meaning of the name Hadad, see 1 Kings 11:14 and 1 Kings 11:23.