Or HaChaim on Deuteronomy 29:15/אור החיים על דברים כ״ט:ט״ו

1 כי אתם ידעתם, "For you know, etc." We need to analyse why the Torah suddenly provides this rationale for what it legislates in this paragraph. Nachmanides wrote that this is the introduction to what follows "so that there not be amongst you a root flourishing with wormwood, etc." I consider this explanation a little forced. It is not the custom of the Torah to write the reason for its legislation before writing the legislation itself. Perhaps the verse may be understood differently. Inasmuch as what is being legislated here is something unique, i.e. obligating unborn generations to observe a code of conduct over which they have never been allowed to make a decision, as had their ancestors at Mount Sinai, this requires an unusual approach. We have a rule in Ketuvot 11 that "one cannot hold a person responsible for committing a wrong which he had never been aware of." According to this principle the acceptance by the parents of the obligation to keep the Torah would not be binding on the children at all. This is why the Torah adds: "for you are aware what your life was like before you became G'd's people and received the Torah, etc." In other words, the Torah is reminding us that it is a privilege to be G'd's people, to keep the Torah, etc. This is not comparable to imposing duties and restrictions on your children. The purpose of a life filled with מצוה-observance is to avoid the pitfalls of the abominations and detestable idols the Egyptians were captive to. Moses tells the people present that inasmuch as they know all about this they also know that what is being asked of them is to confer benefits rather than restrictions on their children and children's children.