Sukkot is the holiday “most closely associated with the Oral Law,” according to Rabbi Joseph Soloveitchik, as so much of the holiday — from identifying “p’ri eitz hadar” [“fruit of goodly trees”] (Lev 23:40) to determining what constitutes a sukkah — is determined via Oral Law (see below). Taking this thought one step further: Throughout this holiday, we dwell, more literally than usual, within a divine-human collaborative construction.
Each year, we erect a new structure resembling the ones our ancestors built but using the materials and hands available to us at the time. Each year, our conception of Torah carries the teachings of our ancestors but makes use of new insights and adaptations to changing circumstances.
Sukkot asks us to dwell, for a time, deeply in shakiness: for some this translates into awareness that all depends, ultimately, on God; for others, the focus is on interdependence with others in living through forces far beyond our control.
In the sukkah we also dwell, for a time, deeply in an awareness of the human, fallible construction of our Torah understanding and of our abilities, individually and collectively, to put Torah into practice.
As we prepare to leave the sukkah, we may hope that next year’s construction will be of even stronger, more beautiful materials erected by even surer hands. But that hope for the future need not throw doubt on the value of this year’s construction or diminish our enjoyment in this year’s dwelling place.
Only through the Oral Law, can we identify the words
פרי עץ הדר with an etrog, the fruit of the citron tree. The Beit HaLevi (Derush 18) suggests that it was on Yom Kippur, when Moses came down with the second Tablets, that the Oral Law was conferred on the people of Israel. But while Yom Kippur commemorates the giving of the Oral Law, Sukkot is the holiday which actually celebrates it. The Sadducees and Pharisees argued about some very basic rules involving the Sukkot festival. Indeed, what is a sukka? What should its height be? From what materials may it be made? The vast majority of the rules of Sukkot are oral traditions from Sinai. Sukkot is therefore the festival of the Oral Law.
— Koren Mesorat HaRav Siddur p.891-893