2 Chronicles 30:17

For there were many in the congregation that were not hallowed; therefore the Levites had the charge of the slaughtering of the passover-lambs for every one not clean, to hallow them unto Jehovah.

2 Chronicles 29:34

Only the priests were too few, and they could not flay all the burnt-offerings; therefore their brethren the Levites helped them, until the work was ended, and until the priests had hallowed themselves; for the Levites were more upright in heart to hallow themselves than the priests.

Exodus 12:6

And ye shall keep it until the fourteenth day of this month; and the whole congregation of the assembly of Israel shall kill it between the two evenings.

2 Chronicles 35:3-6

And he said to the Levites, that taught all Israel, and who were holy to Jehovah, Put the holy ark in the house that Solomon the son of David, king of Israel, built; ye have not to carry it upon your shoulders. Serve now Jehovah 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
Only the priests were too few, and they could not flay all the burnt-offerings; therefore their brethren the Levites helped them, until the work was ended, and until the priests had hallowed themselves; for the Levites were more upright in heart to hallow themselves than the priests.
2 Chronicles 35:3
And he said to the Levites, that taught all Israel, and who were holy to Jehovah, Put the holy ark in the house that Solomon the son of David, king of Israel, built; ye have not to carry it upon your shoulders. Serve now Jehovah your God, and his people Israel;

The killing

Exodus 12:6
And ye shall keep it until the fourteenth day of this month; and the whole congregation of the assembly of Israel shall kill it between the two evenings.