In the days of Jehoram, Edom rebelled against the hand of Judah and appointed their own king.
We find here, I. That Jehoshaphat was a very careful indulgent father to Jehoram. He had many sons, who are here named (Ch2 21:2), and it is said (Ch2 21:13) that they were better than Jehoram, had a great deal more wisdom and virtue, and lived up to their education, which he went counter to.
Commenting on 2 Chronicles 21:1-11
EDOM AND LIBNAH REVOLT. (Ch2 21:8-17) the Edomites revolted--That nation had been made dependent by David, and down to the time of Jehoshaphat was governed by a tributary ruler (Kg1 22:47; Kg2 3:9). But that king having been slain in an insurrection at home, his successor thought to ingratiate himself with his new subjects by raising the flag of independence [JOSEPHUS].
In his days the Edomites revolted - See on Kg2 8:21 (note).