Thematic Bible: Irregularities in

He said to them, "Haven't you read what David did when he and those who were with him were hungry- how he entered the house of God, and they ate the sacred bread, which is not lawful for him or for those with him to eat, but only for the priests?

For the king and his officials and the entire congregation in Jerusalem decided to observe the Passover of the Lord in the second month because they were not able to observe it at the appropriate time, since not enough of the priests had consecrated themselves and the people hadn't been gathered together in Jerusalem. The proposal pleased the king and the congregation, read more.
so they affirmed the proposal and spread the message throughout all Israel, from Beer-sheba to Dan, to come to observe the Passover of the Lord God of Israel in Jerusalem, for they hadn't observed it often, as prescribed.

for there were many in the assembly who had not consecrated themselves, and so the Levites were in charge of slaughtering the Passover [lambs] for every unclean person to consecrate [the lambs] to the Lord. For a large number of the people-many from Ephraim, Manasseh, Issachar, and Zebulun-were unclean, yet they had eaten the Passover contrary to what was written. But Hezekiah had interceded for them, saying, "May the good Lord provide atonement on behalf of whoever sets his whole heart on seeking God, the Lord God of his ancestors, even though not according to the purification [rules] of the sanctuary." read more.
So the Lord heard Hezekiah and healed the people.