Or HaChaim on Exodus 12:24/אור החיים על שמות י״ב:כ״ד

1 ושמרתם את הדבר הזה, "You will observe this matter." According to the plain meaning of this verse the Torah tells that such matters as the sprinkling of the blood of the paschal lamb would also be performed in future generations. However, we have no reports to indicate that these details were ever observed again. We do not find that either the Mishnah or the Talmud ever instituted this as a rabbinic requirement. I believe that the words לחק לך on the one hand, and ולבניך on the other hand, mean that the application of the Passover law is not identical for future generations. As for as you, i.e. the present generation is concerned, all the aforementioned details apply. As to לבניך עד עולם only certain details of the Passover in Egypt will apply. The verse relies on legislation repeated in the Torah elsewhere to arrive at the pertinent observances to be observed in the future. The repetition of the purpose of these observances in Egypt, i.e. to keep the angel of death away from the homes of the Jews makes it plain that certain of the details would not apply in the future when G'd would not kill the firstborns.