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

[153] Now as soon as what concerned Athaliah was by this stratagem, after this manner, despatched, Jehoiada called together the people and the armed men into the temple, and made them take an oath that they would be obedient to the king, and take care of his safety, and of the safety of his government; after which he obliged the king to give security [upon oath] that he would worship God, and not transgress the laws of Moses. They then ran to the house of Baal, which Athaliah and her husband Jehoram had built, to the dishonor of the God of their fathers, and to the honor of Ahab, and demolished it, and slew Mattan, that had his priesthood. But Jehoiada intrusted the care and custody of the temple to the priests and Levites, according to the appointment of king David, and enjoined them to bring their regular burnt-offerings twice a day, and to offer incense according to the law. He also ordained some of the Levites, with the porters, to be a guard to the temple, that no one that was defiled might come there.