Charles Ellicott Commentary 2 Chronicles 21:8

"In his days Edom revolted from under the hand of Judah, and made a king over themselves." — 2 Chronicles 21:8 (ASV)

In his days the Edomites revolted. (2 Kings 8:20). See also 1 Kings 22:47, from which it appears that under Jehoshaphat “a deputy,” or viceroy, ruled in Edom. (Compare to 2 Chronicles 20:35, Note.)