Numbers 8:22

And after that shall the Levites go in to do the service of the tabernacle of the congregation: and thou shalt cleanse them, and offer them for an offering.

Then they killed the passover on the fourteenth day of the second month: and the priests and the Levites were ashamed, and sanctified themselves, and brought in the burnt offerings into the house of the LORD. And they stood in their place after their manner, according to the law of Moses the man of God: the priests sprinkled the blood, which they received of the hand of the Levites. For there were many in the congregation that were not sanctified: therefore the Levites had the charge of the killing of the passovers for every one that was not clean, to sanctify them unto the LORD.

And Hezekiah appointed the courses of the priests and the Levites after their courses, every man according to his service, the priests and Levites for burnt offerings and for peace offerings, to minister, and to give thanks, and to praise in the gates of the tents of the LORD.

And his princes gave willingly unto the people, to the priests, and to the Levites: Hilkiah and Zechariah and Jehiel, rulers of the house of God, gave unto the priests for the passover offerings two thousand and six hundred small cattle and three hundred oxen. Conaniah also, and Shemaiah and Nethaneel, his brethren, and Hashabiah and Jeiel and Jozabad, chief of the Levites, gave unto the Levites for passover offerings five thousand small cattle, and five hundred oxen. So the service was prepared, and the priests stood in their place, and the Levites in their courses, according to the king's commandment. And they killed the passover, and the priests sprinkled the blood from their hands, and the Levites flayed them. And they removed the burnt offerings, that they might give according to the divisions of the families of the people, to offer unto the LORD, as it is written in the book of Moses. And so did they with the oxen. And they roasted the passover with fire according to the ordinance: but the other holy offerings sod they in pots, and in caldrons, and in pans, and divided them speedily among all the people. And afterward they made ready for themselves, and for the priests: because the priests the sons of Aaron were busied in offering of burnt offerings and the fat until night; therefore the Levites prepared for themselves, and for the priests the sons of Aaron. And the singers the sons of Asaph were in their place, according to the commandment of David, and Asaph, and Heman, and Jeduthun the king's seer; and the porters waited at every gate; they might not depart from their service; for their brethren the Levites prepared for them.