2 Chronicles 30:3
but they had been unable to celebrate it then because not enough priests had consecrated themselves and the people had not yet been gathered together in Jerusalem.
2 Chronicles 29:34
Because there weren't enough priests, they were unable to prepare all the burnt offerings until other priests came forward after having consecrated themselves, so their descendant of Levi relatives assisted them until the services were complete. (The descendants of Levi had been more conscientious in consecrating themselves than had been the priests.)
Exodus 12:6
It is to remain under your care until the fourteenth day of this month, and then the entire assembly of the congregation of Israel is to slaughter it at twilight.
Exodus 12:18
In the first month, from the evening of the fourteenth day of the month until the evening of the twenty-first day of the month, you are to eat unleavened bread.
2 Chronicles 29:17
They began their consecration duties on the first day of the first month and finished at the LORD's outer vestibule on the eighth day of the month. Another eight days was used to consecrate the LORD's Temple, so they completed the work on the sixteenth day of the first month.