2 Kings 8:18 - Joseph Benson’s Commentary on the Old and New Testaments

And he walked in the way of the kings of Israel That is, after his father's death. For the daughter of Ahab Namely, Athaliah, 2 Kings 8:26; was his wife By whom he was seduced from the religion of his pious father and grandfather. This unequal marriage, though Jehoshaphat possibly designed it as a means of uniting the two kingdoms under one head, is here and elsewhere noted, as the cause both of the great wickedness of his posterity, and of those sore calamities which befell them. No good could be reasonably expected from such a union. Those that are ill matched are already half ruined.