1 Chronicles 23:30-32

30They were also to stand every morning to thank and praise the Lord. They were to do the same in the evening 31and whenever burnt offerings were presented to the Lord on the Sabbaths, at the New Moon feasts and at the appointed festivals. They were to serve before the Lord regularly in the proper number and in the way prescribed for them. 32And so the Levites carried out their responsibilities for the tent of meeting, for the Holy Place and, under their relatives the descendants of Aaron, for the service of the temple of the Lord.