2 Chronicles 35:15-16

15The singers, the sons of Asaph, were also at their stations 1according to the command of David, Asaph, Heman, and Jeduthun the king’s seer; and 2the gatekeepers at each gate did not have to depart from their service, because the Levites their brethren prepared for them.

16So all the service of the Lord was prepared on that day to celebrate the Passover, and to offer burnt offerings on the altar of the Lord according to the command of King Josiah.