Nehemiah 12:45
And both the singers and the porters kept the ward of their God, and the ward of the purification, according to the commandment of David, and of Solomon his son.
1 Chronicles 25:1-26
Moreover David and the captains of the host separated to the service of the sons of Asaph, and of Heman, and of Jeduthun, who should prophesy with harps, with psalteries, and with cymbals: and the number of the workmen according to their service was:
1 Chronicles 23:28
Because their office was to wait on the sons of Aaron for the service of the house of the LORD, in the courts, and in the chambers, and in the purifying of all holy things, and the work of the service of the house of God;
2 Chronicles 23:6
But let none come into the house of the LORD, save the priests, and they that minister of the Levites; they shall go in, for they are holy: but all the people shall keep the watch of the LORD.