1 Chronicles 23:31

23:31 and whenever burnt sacrifices were offered to the Lord on the Sabbath and at new moon festivals and assemblies. A designated number were to serve before the Lord regularly in accordance with regulations.

1 Chronicles 24:19

24:19 This was the order in which they carried out their assigned responsibilities when they entered the Lord’s temple, according to the regulations given them by their ancestor Aaron, just as the Lord God of Israel had instructed him.