John Gill Commentary 2 Chronicles 18:1

"Now Jehoshaphat had riches and honor in abundance; and he joined affinity with Ahab." — 2 Chronicles 18:1 (ASV)

Now Jehoshaphat has riches and honour in abundance
Still more and more, see (2 Chronicles 17:5) , and which moved Ahab to desire friendship and affinity with him, to which Jehoshaphat agreed:

and joined affinity with Ahab ;
king of Israel, married his son Joram to Athaliah, a daughter of Ahab by Jezebel of Zidon; which marriage proved of bad consequence to Jehoshaphat and his family.