Numbers 9:3-5

King James Version

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.