Nitzavim-Vayelech 5773

Moshe brings Bnei Yisroel into a covenant with Hashem, adding that it will include "those who aren't with us today" (29:13). Rashi says this means to include future generations. But how can it be possible to include these future generations? The Sifsei Chachamim explains that a father's child is like his own leg; they are interconnected to the point that when the father accepts the covenant, the child is included in it.