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

[253] Costobarus was an Idumean by birth, and one of principal dignity among them, and one whose ancestors had been priests to the Koze, whom the Idumeans had [formerly] esteemed as a god; but after Hyrcanus had made a change in their political government, and made them receive the Jewish customs and law, Herod made Costobarus governor of Idumea and Gaza, and gave him his sister Salome to wife; and this was upon the slaughter of [his uncle] Joseph, who had that government before, as we have related already. When Costobarus had gotten to be so highly advanced, it pleased him and was more than he hoped for, and he was more and more puffed up by his good success, and in a little while he exceeded all bounds, and did not think fit to obey what Herod, as their ruler, commanded him, or that the Idumeans should make use of the Jewish customs, or be subject to them. He therefore sent to Cleopatra, and informed her that the Idumeans had been always under his progenitors, and that for the same reason it was but just that she should desire that country for him of Antony, for that he was ready to transfer his friendship to her; and this he did, not because he was better pleased to be under Cleopatra's government, but because he thought that, upon the diminution of Herod's power, it would not be difficult for him to obtain himself the entire government over the Idumeans, and somewhat more also; for he raised his hopes still higher, as having no small pretenses, both by his birth and by these riches which he had gotten by his constant attention to filthy lucre; and accordingly it was not a small matter that he aimed at. So Cleopatra desired this country of Antony, but failed of her purpose. An account of this was brought to Herod, who was thereupon ready to kill Costobarus; yet, upon the entreaties of his sister and mother, he forgave him, and vouchsafed to pardon him entirely; though he still had a suspicion of him afterward for this his attempt.