Or HaChaim on Exodus 12:43/אור החיים על שמות י״ב:מ״ג

1 ויאמר ה׳…זאת חוקת הפסח, G'd said: "this is the statute of the Passover, etc." It is puzzling why this verse does not follow the usual procedure of introducing a direct commandment, i.e. "speak to the children of Israel, etc." According to what we wrote on verse 3 that this paragraph was said on the 14th of Nissan there was no need to write: "speak to the children of Israel" because it is a continuation of what is written in verse 3, i.e. "speak to the whole community, etc." We must explain then why this paragraph is not recorded as part of what Moses said in that verse. The answer is that this whole commandment is designed for observance of the Passover in future generations only, hence it was revealed after the Exodus. The principle reason for the legislation is to inform Israel that every detail mentioned here is essential for performance of the Passover in the future.

2I have seen a view expressed in Shemot Rabbah 19,5 according to which G'd despatched a special wind from Paradise which lent its fragrance to Moses' Passover. When the Israelites inhaled this fragrance they all begged Moses to allow them a taste of his Passover lamb. Moses replied they could not do this as they had not been circumcised, seeing it states in our verse that you have to be circumcised in order to eat from the Passover. Thereupon the Israelites performed the rite of circumcision upon themselves. According to this Midrash we can easily explain why the Torah here did not write: "speak to the children of Israel, etc." An alternative explanation is that this paragraph was addressed only to Moses and Aaron and that G'd commanded them that uncircumcised people should not eat from the Passover. After the Israelites came to Moses and wanted to eat from his Passover they decided to circumcise themselves. [after all the commandment to circumcise themselves dated back to Abrahamitic times and was not valid only for consumption of the Passover. Ed.]

3According to the aforementioned Midrash how was it possible that Moses would let everyone partake of his Passover seeing it could only be eaten by people who had been invited prior to its being slaughtered? Perhaps Moses only promised them that they could eat from it in order to encourage them to perform circumcision. As soon as the Israelites had circumcised themselves they found that their own Passover exuded the same fragrance as that of Moses so that they did not need to ask him to share it with them. I have seen a proof that the words of that Midrash are true, i.e. that the Israelites had not been prepared to circumcise themselves up to that point. We read in Ezekiel 20,8: "they rebelled against Me and did not want to listen to Me, and I threatened to pour out My wrath over them in the land of Egypt." Clearly, the prophet speaks of the Israelites' unwillingness to observe even the few commandments of G'd which applied at that time, primarily that of circumcision.