Numbers 9:1-5King James Version (KJV)
9 And the Lord spake unto Moses in the wilderness of Sinai, in the first month of the second year after they were come out of the land of Egypt, saying,
2 Let the children of Israel also keep the passover at his appointed season.
3 In the fourteenth day of this month, at even, ye shall keep it in his appointed season: according to all the rites of it, and according to all the ceremonies thereof, shall ye keep it.
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.