In his days Edom revolted against Judah's authority, and made a king over themselves.
2 Chronicles 21:8
Surrounding context
21:7 Yet the LORD would not destroy the house of David, because of the covenant that He had made with David, and since He had promised to give a lamp to him and to his sons forever.
21:8 In his days Edom revolted against Judah's authority, and made a king over themselves.
21:9 So Jehoram went out with his officers, and all his chariots with him. And he rose by night and attacked the Edomites who had surrounded him and the captains of the chariots.