Nehemiah

And said unto them, Hear me, ye Levites, sanctify now yourselves, and sanctify the house of the Lord God of your fathers, and carry forth the filthiness out of the holy place.

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;

And that we should bring the firstfruits of our dough, and our offerings, and the fruit of all manner of trees, of wine and of oil, unto the priests, to the chambers of the house of our God; and the tithes of our ground unto the Levites, that the same Levites might have the tithes in all the cities of our tillage.

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.

And they gathered their brethren, and sanctified themselves, and came, according to the commandment of the king, by the words of the Lord, to cleanse the house of the Lord.