2 Chronicles 30:17
For there were many in the assembly who had not consecrated themselves [that is, become ceremonially clean and free from all sin]; so the Levites had to slaughter the Passover lambs for everyone who was not clean, in order to make them holy for the Lord.
2 Chronicles 29:34
But there were too few priests and they were unable to skin all the burnt offerings; so until the other priests had consecrated themselves, their brothers, the Levites, helped them until the work was done. For the Levites were more upright in heart and more conscientious than the priests in consecrating themselves.
Exodus 12:6
You shall keep it until the fourteenth day of the same month, then the whole assembly of the congregation of Israel is to slaughter it
2 Chronicles 35:3-6
To the Levites who taught all Israel and were holy to the Lord he said, “Put the holy ark in the house (temple) which Solomon the son of David king of Israel built; it shall not be a burden [carried] on your shoulders any longer. Now serve the Lord your God and His people Israel.