I was listening to a shiur by R’ Hershel Shachter on P’ VaYakhel and he referenced an interesting Yalkut Shimoni at the beginning of VaYakhel (here) which notes that this is the only parsha which begins with Moshe calling a gathering of all the people together. The purpose of the gathering was to publicly teach hilchos shabbos, which served as a lesson for future generations that shabbos should be spent gathered together in the bais medrash learning the inyana d’yoma, hilchos shabbos. This takana is an extension of the takana of Moshe Rabeinu mentioned at the end of Mes. Megillah to study the halachos of each Yom Tov on that respective Yom Tov, .i.e. hilchos pesach b’pesach, hilchos chag b’chag – according to the Midrash, inyanei shabbos should be learned on shabbos as well. (I was wondering if this is the source of the practice of gedolim like the GR"A and R' Tzvi Pesach Frank who would finish Masechet Shabbos each Shabbos).
By coincidence my son is also making a siyum on Mes. Megillah, and IY”H will be speaking about this takanah. Chazal teachesthat it is a mitzvah to study (shoalin v’dorshin) the laws of each Yom Tov thirty days before the chag (Pesachim 6a). The Sha’gas Arye (and others) ask, if there already exists a takanah to study the halachos thirty days before Yom Tov, why is an additional takanah to study the halacha on the day of Y”T itself necessary?
The Ran is medayek in the words shoalin v’dorshin, we ask about the halachos and explain them. Ran writes that this takanah is not an obligation to study halacha, but a direction to poskim and Rabbis as to how to prioritize questions. Within thirty days before a Yom Tov any query that relates to the upcoming holiday takes precedence over other questions and research. The takanah referred to at the end of Mes. Megillah is a separate din that teaches that one should study the laws of Yom Tov on the day of the holiday itself.
The majority of Rishonim (see Biur Halacha, O.C. 429), however, do not learn like the Ran and explain shoalin v’dorshin simply as an obligation to study halachos. According to this reading, the question of overlapping takanos remains. Stay tuned for more...