What exactly was "contrary to what was written" in 2 Chronicles 30:18?

Question

Numbers 9:6-14 talks about some israelites that were unclean but still wanted to celebrate the Passover. They asked Moses if they could, and Moses asked God, and God said (verse 10, NIV):

... When any of you or your descendants are unclean because of a dead body or are away on a journey, they are still to celebrate the LORD's Passover.

We see a similar situation in 2 Chronicles 30:17-20, in which some israelites that had not purified themselves ate the Passover, but the author says (verse 18, NIV):

Although most of the many people who came from Ephraim, Manasseh, Issachar and Zebulun had not purified themselves, yet they ate the Passover, contrary to what was written.

Then king Hezekiah prayed for them, etc.

How is that contrary to what was written?

Answer 1

The question is answered by understanding the first misunderstanding. The passage from Numbers 9 does not end with God saying they should go ahead and eat while unclean.

Numbers 9 (NASB) 6 But there were some men who were unclean because of the dead person, so that they could not observe Passover on that day; so they came before Moses and Aaron on that day.
7 Those men said to him, "Though we are unclean because of the dead person, why are we restrained from presenting the offering of the LORD at its appointed time among the sons of Israel?"
8 Moses therefore said to them, "Wait, and I will listen to what the LORD will command concerning you."
9 Then the LORD spoke to Moses, saying,
10 "Speak to the sons of Israel, saying, 'If any one of you or of your generations becomes unclean because of a dead person, or is on a distant journey, he may, however, observe the Passover to the LORD.
11 'In the second month on the fourteenth day at twilight, they shall observe it; they shall eat it with unleavened bread and bitter herbs.

They are to observe the Passover the next month on the 14th.