2 Chronicles 30:17

For there were many in the assembly who had not consecrated themselves; therefore, the Levites were over the slaughter of the Passover lambs for everyone who was unclean, in order to consecrate them to the Lord.

2 Chronicles 29:34

But the priests were too few, so that they were unable to skin all the burnt offerings; therefore their brothers the Levites helped them until the work was completed and until the other priests had consecrated themselves. For the Levites were more conscientious to consecrate themselves than the priests.

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 kill it at twilight.

2 Chronicles 35:3-6

He also said to the Levites who taught all Israel and who were holy to the Lord, “Put the holy ark in the house which Solomon the son of David king of Israel built; it will be a burden on your shoulders no longer. Now serve the Lord your God and His people Israel.

Treasury of Scripture Knowledge

Summary

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.

The killing

Bible References

The levites

2 Chronicles 29:34
But the priests were too few, so that they were unable to skin all the burnt offerings; therefore their brothers the Levites helped them until the work was completed and until the other priests had consecrated themselves. For the Levites were more conscientious to consecrate themselves than the priests.
2 Chronicles 35:3
He also said to the Levites who taught all Israel and who were holy to the Lord, “Put the holy ark in the house which Solomon the son of David king of Israel built; it will be a burden on your shoulders no longer. Now serve the Lord your God and His people Israel.

The killing

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 kill it at twilight.