Worshiping Wrongly

The nation of Israel had failed, for a long time, to keep the Passover "according to the way it was written". When King Hezekiah tried to turn the nation back to God, he hosted a Passover party like hadn't been seen in years.

 

However, because "the thing was done suddenly", there weren't enough sanctified priests to serve the need, because they were lax in sanctifying themselves, so their brothers helped them.

WEB 2 Chron 29:34 But the priests were too few, so that they could not skin all the burnt offerings. Therefore their brothers the Levites helped them, until the work was ended, and until the priests had sanctified themselves; for the Levites were more upright in heart to sanctify themselves than the priests.

Also, the Passover was to be kept in the first month of the year, but because they weren't ready, they made their own decision to keep it in the second month.

2 Chron 30:2 For the king had taken counsel with his princes and all the assembly in Jerusalem to keep the Passover in the second month. 3 For they could not keep it at that time, because the priests had not sanctified themselves in sufficient number, and the people had not gathered themselves together to Jerusalem. 4 The thing was right in the eyes of the king and of all the assembly. 5 So they established a decree to make proclamation throughout all Israel, from Beersheba even to Dan, that they should come to keep the Passover to Yahweh, the God of Israel, at Jerusalem, for they had not kept it in great numbers in the way it is written.

And third, the people themselves were not properly sanctified for the festivities:

2 Chron 30:17 For there were many in the assembly who had not sanctified themselves: therefore the Levites were in charge of killing the Passovers for everyone who was not clean, to sanctify them to Yahweh. 18 For a multitude of the people, even many of Ephraim, Manasseh, Issachar, and Zebulun, had not cleansed themselves,

And yet, the priests were ashamed of their failure, and the people who came humbled themselves:

2 Chron 30:11 Nevertheless some men of Asher, Manasseh, and Zebulun humbled themselves, and came to Jerusalem. ... 15 Then they killed the Passover on the fourteenth day of the second month. The priests and the Levites were ashamed, and sanctified themselves, and brought burnt offerings into Yahweh’s house.

And King Hezekiah prayed for the people, even though they didn't do things in the right way:

2 Chron 30:18 For a multitude of the people, even many of Ephraim, Manasseh, Issachar, and Zebulun, had not cleansed themselves, yet they ate the Passover other than the way it is written. For Hezekiah had prayed for them, saying, “May the good Yahweh pardon everyone 19 who sets his heart to seek God, Yahweh, the God of his fathers, even if they aren’t clean according to the purification of the sanctuary.”

And the result?

2 Chron 30:20 Yahweh listened to Hezekiah, and healed the people. ... 27 Then the Levitical priests arose and blessed the people. Their voice was heard, and their prayer came up to his holy habitation, even to heaven.