2 Chronicles 30:3

For they could not do it at that time for the priests consecrated not themselves sufficiently, and the people were not gathered to Jerusalem.

2 Chronicles 29:34

Only the priests were for fewness and they could not slaughter all the burnt-offerings: and their brethren the Levites will strengthen them till the finishing of the work, and till the priests shall consecrate themselves: for the Levites being upright of heart to consecrate themselves more than the priests.

Exodus 12:6

And it shall be to you for a preservation till the fourteenth day of this month; and they shall slaughter it, all the convocation of the assembly of Israel, between the two evenings.

Exodus 12:18

In the first, in the fourteenth day of the month, in the evening, ye shall eat unleavened till the one and twentieth day of the month in the evening.

2 Chronicles 29:17

And they will begin in one to the first month to consecrate, and in the eighth day to the month they came to the porch of Jehovah: and they will consecrate the house of Jehovah for eight days; and in the sixteenth day to the first month they finished.

Treasury of Scripture Knowledge

Summary

For they could not keep it at that time, because the priests had not sanctified themselves sufficiently, neither had the people gathered themselves together to Jerusalem.

At that time

Bible References

At that time

Exodus 12:6
And it shall be to you for a preservation till the fourteenth day of this month; and they shall slaughter it, all the convocation of the assembly of Israel, between the two evenings.

Because

2 Chronicles 29:34
Only the priests were for fewness and they could not slaughter all the burnt-offerings: and their brethren the Levites will strengthen them till the finishing of the work, and till the priests shall consecrate themselves: for the Levites being upright of heart to consecrate themselves more than the priests.