“They shall live in the sukkot for seven days; every citizen in Israel shall live in the sukkot. So that your generations will know that in the sukkot I had Bnei Yisrael live when I took them out of the Land of Egypt; I am Hashem, your G-d” (Vayikra 23:42-43). In the midrash (Sifra, Emor 12) we find three explanations for this mitzva. There is an opinion that the sukka is to be made from the four species which are waved on Sukkot, which implies that it is essentially part of one unit with the mitzva of the four species. It is difficult, though, to divorce the mitzva from the historical context to which the p’sukim refer explicitly.