2 Chronicles 30:18
For a multitude of the people, even many of Ephraim, and Manasseh, Issachar, and Zebulun, had not cleansed themselves, yet did they eat the passover otherwise than it was written. But Hezekiah prayed for them, saying, The good LORD pardon every one
The verse belongs to Hezekiah's first Passover in Jerusalem, held after the idolatrous shrines had been cleared away. During that Passover week provision was made for the priests and Levites to read the book of the law publicly and teach the people each day, while the people spent the week offering peace offerings and learning what God required. Observing the statutes given through Moses, especially those in the book of the covenant, was connected with the prosperity of Hezekiah's reign.
Later Manasseh set those statutes aside and the temple copy of the law was lost, leaving the people without its instruction for many years. A multitude who came to keep the Passover had not cleansed or purified themselves according to the law, yet they ate the Passover otherwise than it was written. Hezekiah prayed for pardon for everyone who had prepared or set the heart to seek God though not ceremonially clean, and the Lord heard Hezekiah and pardoned and healed the people.
That mercy filled the united multitude with great gladness and daily praise to God as gracious and merciful. The verse addresses the position of God's people in the present time and calls people of every age, including children, to give themselves wholly to the Lord.