2 Chronicles 29:16 (KJV)

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.

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.

Then Hezekiah the king rose early, and gathered the rulers of the city, and went up to the house of the LORD.

And they brought seven bullocks, and seven rams, and seven lambs, and seven he goats, for a sin offering for the kingdom, and for the sanctuary, and for Judah. And he commanded the priests the sons of Aaron to offer them on the altar of the LORD.