Nehemiah 13:9

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. For our fathers have trespassed, and done that which was evil in the eyes of the LORD our God, and have forsaken him, and have turned away their faces from the habitation of the LORD, and turned their backs. Also they have shut up the doors of the porch, and put out the lamps, and have not burned incense nor offered burnt offerings in the holy place unto the God of Israel. Wherefore the wrath of the LORD was upon Judah and Jerusalem, and he hath delivered them to trouble, to astonishment, and to hissing, as ye see with your eyes. For, lo, our fathers have fallen by the sword, and our sons and our daughters and our wives are in captivity for this. Now it is in mine heart to make a covenant with the LORD God of Israel, that his fierce wrath may turn away from us. My sons, be not now negligent: for the LORD hath chosen you to stand before him, to serve him, and that ye should minister unto him, and burn incense. Then the Levites arose, Mahath the son of Amasai, and Joel the son of Azariah, of the sons of the Kohathites: and of the sons of Merari, Kish the son of Abdi, and Azariah the son of Jehalelel: and of the Gershonites; Joah the son of Zimmah, and Eden the son of Joah: And of the sons of Elizaphan; Shimri, and Jeiel: and of the sons of Asaph; Zechariah, and Mattaniah: And of the sons of Heman; Jehiel, and Shimei: and of the sons of Jeduthun; Shemaiah, and Uzziel. 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. And the priests went into the inner part of the house of the LORD, to cleanse it, and brought out all the uncleanness that they found in the temple of the LORD into the court of the house of the LORD. And the Levites took it, to carry it out abroad into the brook Kidron. Now they began on the first day of the first month to sanctify, and on the eighth day of the month came they to the porch of the LORD: so they sanctified the house of the LORD in eight days; and in the sixteenth day of the first month they made an end. Then they went in to Hezekiah the king, and said, We have cleansed all the house of the LORD, and the altar of burnt offering, with all the vessels thereof, and the shewbread table, with all the vessels thereof. Moreover all the vessels, which king Ahaz in his reign did cast away in his transgression, have we prepared and sanctified, and, behold, they are before the altar of the LORD.

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.