1 Chronicles 23:4-5, 28-32

Of these 24,000 were to oversee and inspect the work of the house of the LORD and 6,000 were to be administrators and judges, and 4,000 were gatekeepers, and 4,000 [musicians] were to praise the LORD with the instruments which David made for giving praise.

For their duty is to assist [the priests] the sons of Aaron in the service of the house of the LORD, in [caring for] the courtyards, the chambers, the purifying of all holy things, and any work of the service of the house of God, and with the showbread, and the fine flour for a grain offering, and unleavened wafers, or what is baked in the pan or what is well-mixed, and all measures of volume and size [as the Law of Moses required]. They are to stand every morning to thank and praise the LORD, and likewise at evening, and to offer all burnt sacrifices to the LORD on the Sabbaths, the new moons, and the festivals by number according to the ordinance concerning them, continually before the LORD. So they shall be responsible for the Tent of Meeting, the Holy Place, and the sons of Aaron their relatives, for the service of the house of the LORD.