2 Chronicles 35:15

And with regard to the musicians, the sons of Asaph, who were in their station, according to the commands of David, both Asaph and Aiman and Idithun the king’s prophets; and the chiefs and the keepers of the gates, they were not at liberty to move from their holy services, for their brethren the Levites prepared for them.

And the sons of Asaph the psalm-singers were at their post according to the commands of David, and Asaph, and Æman, and Idithom, the prophets of the king: also the chiefs and the porters of the several gates;—it was not for them to stir from the service of the holy things, for their brethren the Levites prepared for them.