Numbers 9:5

2 Let the children of Israel keep the Passover at its regular time.

3 In the fourteenth day of this month, at evening, you are to keep it at the regular time, and in the way ordered in the law.

4 And Moses gave orders to the children of Israel to keep the Passover.

5 So they kept the Passover in the first month, on the fourteenth day of the month, at evening, in the waste land of Sinai: as the Lord gave orders to Moses, so the children of Israel did.

6 And there were certain men who were unclean because of a dead body, so that they were not able to keep the Passover on that day; and they came before Moses and before Aaron on that day:

7 And these men said to him, We have been made unclean by the dead body of a man; why may we not make the offering of the Lord at the regular time among the children of Israel?

8 And Moses said to them, Do nothing till the Lord gives me directions about you.