Nehemiah 12:45
And they kept the ward of their God and the ward of the purification, and the singers and the porters, according to the statute of David and of Solomon, his son.
1 Chronicles 25:1-26
Moreover David and the captains of the host separated unto the ministry the sons of Asaph and of Heman and of Jeduthun, who should prophesy with harps, with psalteries, and with cymbals; and the number of men that were suitable for the work of their respective ministry was,
1 Chronicles 23:28
And their station was at the hand of 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 in the work of the ministry of the house of God,
2 Chronicles 23:6
But let no one come into the house of the LORD, except the priests and the Levites that minister; they shall go in, for they are holy; but all the people shall keep the watch of the LORD.