Charles Ellicott Commentary 2 Kings 8:20

"In his days Edom revolted from under the hand of Judah, and made a king over themselves." — 2 Kings 8:20 (ASV)

In his days Edom revolted. —The connection of ideas is this: Although Jehovah was not willing to destroy Judah completely, yet He allowed it to be seriously weakened by the defections recorded in 2 Kings 8:20–22.

Made a king over themselves. —Josephus says they killed the vassal king appointed over them by Jehoshaphat (1 Kings 22:48). Edom appears to have been subject to the hegemony of Judah from the time of the disruption under Rehoboam.