2 Chronicles 35:14-15

14Afterward, they made preparations for themselves and for the kohanim, because the kohanim, the sons of Aaron, were busy sacrificing the burnt offerings and the fat until nightfall. So the Levites made preparations for themselves and for the kohanim, the sons of Aaron.

15The singers, the descendants of Asaph, were at their stations according to the commandment of David, Asaph, Heman and Jeduthun, the king’s seer. The gatekeepers were at every gate. They did not need to depart from their posts for their fellow Levites provided for them.