2 Chronicles 35:14-15

14Afterward, they made preparations for themselves and for the priests, since the priests, the descendants of Aaron, were offering up burnt offerings and fat until nightfall. So the Levites made preparations for themselves and for the priests, the descendants of Aaron.

15The singers, the descendants of Asaph, were at their stations according to the command of David, Asaph, Heman, and Jeduthun the king’s seer. And the gatekeepers at each gate did not need to leave their posts, because their fellow Levites made preparations for them.