2 Chronicles 30:17
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. 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 episode described belongs to the account of Hezekiah's first Passover. That celebration was part of the religious reform carried out during his reign. It took place nearly a century before the reign of Josiah.
That Passover was connected with renewed public attention to the law of Moses. Its statutes were taught to the people by the priests. Observing those statutes of Moses helped make Hezekiah's reign prosperous.