Flavius Josephus, Antiquities of the Jews
William Whiston, A.M., Ed.

[95] Now Jehoram the king of Jerusalem, for we have said before that he had the same name with the king of Israel, as soon as he had taken the government upon him, betook himself to the slaughter of his brethren, and his father's friends, who were governors under him, and thence made a beginning and a demonstration of his wickedness; nor was he at all better than those kings of Israel who at first transgressed against the laws of their country, and of the Hebrews, and against God's worship. And it was Athaliah, the daughter of Ahab, whom he had married, who taught him to be a bad man in other respects, and also to worship foreign gods. Now God would not quite root out this family, because of the promise he had made to David. However, Jehoram did not leave off the introduction of new sorts of customs to the propagation of impiety, and to the ruin of the customs of his own country. And when the Edomites about that time had revolted from him, and slain their former king, who was in subjection to his father, and had set up one of their own choosing, Jehoram fell upon the land of Edom, with the horsemen that were about him, and the chariots, by night, and destroyed those that lay near to his own kingdom, but did not proceed further. However, this expedition did him no service, for they all revolted from him, with those that dwelt in the country of Libnah. He was indeed so mad as to compel the people to go up to the high places of the mountains, and worship foreign gods.