By Rabbi Berach Steinfeld
The posuk in Devorim, Perek Tes Zayin, Posuk Chof Alef says that one should not plant an “asheira tree” next to the mizbayach of Hashem.
Rashi says that we learn from this posuk that one may not plant a tree or build a house on Har Habayis. The Chinuch argues this point in mitzvah taf tzaddik bais when he says that this issur only applies to the azarah.
The Yalkut Shimoni says regarding the above posuk that the issur of building a house includes the issur of building a sukkah. When the Kohanim ate the lechem hapanim on Sukkos, they did so out of the sukkah. The Kohanim were exempt from eating in the sukkah since building a sukkah in the bais hamikdosh is forbidden. The Yalkut Shimoni reconciles the contradiction in two pesukim. The first posuk says that one should build a sukkah for yourself. The other posuk says that one should build a sukkah for Hashem. The first posuk is referring to a private person and the second is referring to eating foods like korbanos of Hashem in the Sukkah. This would seem to contradict what was said above that the lechem hapanim was eaten out of the sukkah. This can be explained by saying that the eating of korbanos which may be eaten across the whole city of Yerushalayim (like the breads of the Korban Toda) would require a sukkah; whereas the breads of the lechem hapanim, which can only be eaten in the bais hamikdosh, has to be eaten out of the sukkah.
The question arises; why is a sukkah forbidden to be built if it is only a temporary dwelling, a “diras arai”? We see from this that even building something that is detached and temporary is forbidden in the Bais Hamikdash. One could argue that it is possible that we pasken like Reb Yehuda who says that a sukkah needs to be a “diras keva” and therefore in this case one would be able to build and then eat in a “diras arai.”
We could argue that it would be forbidden even according to the Rabbanan who are of the opinion that a Sukkah needs to be aria, yet it would be forbidden to be built in the bais hamikdosh. The reasoning for this would be that since one is required to build such a diras arai and needs it in order to be mekayem the mitzvah; therefore that ability to be mekayem the mitzvah makes it like a diras keva and would be forbidden to be built in the bais hamikdosh. This would be comparable to the halacha that tefillin does not need a kesher shel kayama, but nevertheless is forbidden to be tied on Shabbos because rendering something fit for the mitzvah makes it like a kesher shel kayama.
Let us hope that the bais hamikdosh is re-built and we will find out what will be done on Sukkos.