Numbers 9:3-5

9:3 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. 9:4 And Moses spake unto the children of Israel, that they should keep the passover. 9:5 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.