Numbers 9:4-6

King James Version

⁴ And Moses spake unto the children of Israel, that they should keep the passover.

⁵ And they kept the passover on the fourteenth day of the first month at even in the wilderness of Sinai: according to all that the Lord commanded Moses, so did the children of Israel.

⁶ And there were certain men, who were defiled by the dead body of a man, that they could not keep the passover on that day: and they came before Moses and before Aaron on that day: