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

[143] Now, on the Seventh year, Jehoiada communicated the matter to certain of the captains of hundreds, five in number, and persuaded them to be assisting to what attempts he was making against Athaliah, and to join with him in asserting the kingdom to the child. He also received such oaths from them as are proper to secure those that assist one another from the fear of discovery; and he was then of good hope that they should depose Athaliah. Now those men whom Jehoiada the priest had taken to be his partners went into all the country, and gathered together the priests and the Levites, and the heads of the tribes out of it, and came and brought them to Jerusalem to the high priest. So he demanded the security of an oath of them, to keep private whatsoever he should discover to them, which required both their silence and their assistance. So when they had taken the oath, and had thereby made it safe for him to speak, he produced the child that he had brought up of the family of David, and said to them, "This is your king, of that house which you know God hath foretold should reign over you for all time to come. I exhort you therefore that one-third part of you guard him in the temple, and that a fourth part keep watch at all the gates of the temple, and that the next part of you keep guard at the gate which opens and leads to the king's palace, and let the rest of the multitude be unarmed in the temple, and let no armed person go into the temple, but the priest only." He also gave them this order besides, "That a part of the priests and the Levites should be about the king himself, and be a guard to him, with their drawn swords, and to kill that man immediately, whoever he be, that should be so bold as to enter armed into the temple; and bid them be afraid of nobody, but persevere in guarding the king." So these men obeyed what the high priest advised them to, and declared the reality of their resolution by their actions. Jehoiada also opened that armory which David had made in the temple, and distributed to the captains of hundreds, as also to the priests and Levites, all the spears and quivers, and what kind of weapons soever it contained, and set them armed in a circle round about the temple, so as to touch one another's hands, and by that means excluding those from entering that ought not to enter. So they brought the child into the midst of them, and put on him the royal crown, and Jehoiada anointed him with the oil, and made him king; and the multitude rejoiced, and made a noise, and cried, "God save the king!"