There was then no king in Edom: a deputy was king.
The verse stands in a chapter that continues the story of the weak and wicked reign of Ahab. That chapter introduces Jehoshaphat, the good king of Judah, and records his fearful mistake in allying himself with Ahab. It also records the death of Ahab, touches lightly on the reign of Jehoshaphat, and portrays the wickedness of Ahab's son Ahaziah. Within that larger setting the verse belongs to the account of Jehoshaphat's reign in Judah, which was a good reign compromised by his alliance with Ahab and his house.
The verse stands in a chapter that continues the story of the weak and wicked reign of Ahab. That chapter introduces Jehoshaphat, the good king of Judah, and records his fearful mistake in allying himself with Ahab. It also records the death of Ahab, touches lightly on the reign of Jehoshaphat, and portrays the wickedness of Ahab's son Ahaziah. Within that larger setting the verse belongs to the account of Jehoshaphat's reign in Judah, which was a good reign compromised by his alliance with Ahab and his house.