Numbers 9:4-6

Young's Literal Translation

⁴ And Moses speaketh unto the sons of Israel to prepare the passover,

⁵ and they prepare the passover in the first [month], on the fourteenth day of the month, between the evenings, in the wilderness of Sinai; according to all that Jehovah hath commanded Moses, so have the sons of Israel done.

⁶ And there are men who have been defiled by the body of a man, and they have not been able to prepare the passover on that day, and they come near before Moses, and before Aaron, on that day,