2 Chronicles 30:3
For they could not keep it at that time, because the priests had not made themselves pure enough, nor had the people gathered to Jerusalem.
2 Chronicles 29:34
But the priests were too few, so that they could not skin all the burnt offerings. And their brothers the Levites helped them until the work was ended, and until the priests had sanctified themselves. For the Levites were more upright of heart to make themselves pure than the priests.
Exodus 12:6
And you shall keep it up until the fourteenth day of the same month. And the whole assembly of the congregation of Israel shall kill it in the evening.
Exodus 12:18
In the first month, on the fourteenth day of the month at evening, you shall eat unleavened bread, until the twenty-first day of the month at evening.
2 Chronicles 29:17
And they began to sanctify on the first of the first month. And on the eighth day of the month they came to the porch of Jehovah. And they made the house of Jehovah pure in eight days, and in the sixteenth day of the first month they made an end.