Exodus 12:43

AND THE ETERNAL SAID UNTO MOSES AND AARON: THIS IS THE ORDINANCE OF THE PASSOVER. “This chapter was related to them on the fourteenth day of Nisan.” Thus the language of Rashi. This is correct, since at the end of this chapter it is written, Thus did all the children of Israel, as the Eternal hath commanded, attesting concerning them that they and their servants were circumcised, [as this is a prerequisite for eating the Passover-offering]. But if so, Scripture should have logically mentioned this chapter before the section, And it came to pass at midnight. But the reason [the section of the ordinance of the Passover is placed here] is as follows: The chapter of This month shall be unto you the beginning of months, Verse 2. was said on the first of the month. Immediately on that day, Moses fulfilled his mission, [as it states], Then Moses called for all the elders of Israel, and said unto them, meaning that he commanded them concerning the ordinance of the Passover [mentioned here], and he assured them that they will be redeemed on the night of the fifteenth day [of Nisan]. They believed, and the people bowed the head and worshipped., Verse 27. To this account Scripture adjoined the section, And it came to pass at midnight, in order to state that He fulfilled the promise He made to them. On finishing this section, Scripture then reverts to the first theme in order to complete the ordinance of the Passover.
This chapter adds many commandments [concerning the Passover-offering]: the prohibitions of an alien or an uncircumcised Israelite eating thereof, the prohibitions of removing the flesh thereof from where it is eaten and of breaking any of its bones, and the law of the Passover-offering of a proselyte. These commandments applied immediately and for all generations. Then Scripture completed the section by saying that the children of Israel did all this; as G-d commanded… so did they. It uses the expression, all the children of Israel, in order to explain that there was not one person who transgressed the command of G-d concerning all these matters [mentioned here in the section beginning, This is the ordinance of the Passover], as well as all He commanded regarding the laws of the Passover mentioned in the sections above.
Rabbi Abraham ibn Ezra wrote that this chapter dealing with the Passover of the generations, [as distinguished from the Passover of Egypt], was said after the Passover of Egypt, and the verse, Thus did all the children of Israel, refers to the Passover in the wilderness, which they observed in the second year after the exodus. [Although it should logically precede the Passover in the wilderness, according to Ibn Ezra] it is written here because of the general commandment [on the Passover here], the case being similar [to that of the jar of manna which Aaron was to put up before the Testimony in the Tabernacle, of which Scripture says], And Aaron laid it up before the Testimony, for a charge. [This account should logically follow that of the building of the Tabernacle, but instead it was mentioned in the chapter dealing with the manna in order to complete the subject.]
This opinion [of Ibn Ezra here] is a mistake. The commandments in all these chapters deal only with the Passover of Egypt and the Passovers which they were to observe in the Land of Israel, as it is said above, And it shall come to pass, when ye be come to the Land, etc. The Passover in the wilderness, however, was a commandment only for that particular time.

זאת חקת הפסח, for the generations following the Exodus. The Torah legislates where it is to be eaten, by whom, how, when, etc. Only the requirement to put the blood of the sacrificial animal on the doorposts and to eat it in haste, ready for marching, were commandments applicable to the first such offering. All the other ordinances would apply for all future times. (compare Pessachim 96)