In this weeks parsha the Torah commands us to destroy places of avoda zara, and not to do so to Hashem our God (Devarim 12:4). Rashi quotes the Sifri that says that the pasuk is also prohibiting one from destroying any part of the Mezbeiach.
The Rambam (Sefer Hamitzvos Lo Sassei 65 in the short count) says that one is prohibited from destroying the Beis Hamikdash or a beis knesses or beis midrash…as the pasuk states… (Devarim 12:4). The basic reading of this Rambam implies that destroying a beis knesses or beis midrash falls under the prohibition m’d’Oraisa of destroying the Beis Hamikdash.
As a side note, one is only prohibited to destroy in a destructive manner. A repair that requires one to demolish in order to rebuild is permitted.
In fact there are other Rishonim who explicitly state that destroying a shul is prohibited m’d’Oraisa. The Mordechai in Megillah (4:826) says that a shul is considered a Mikdash m’at (small satellite mikdash) and therefore the prohibition to destroy the Beis Hamikdash applies to it as well. This opinion is codified by the Beis Yosef (Orach Chaim 151) and by the Rema (Orach Chaim 152).
The source for this comparison is the Gemara in Megillah 29a that cites the pasuk in Yechezkel that Hashem will be for us a mikdash m’at in galus. The Gemara explains that this refers to batei knessiyos and batei medrashim. We see that in galus, a shul and a beis medrash serve as a mikdash m’at.
Others opine that the prohibition not to destroy a shul is not m’d’Oraisa but m’d’Rabanan. The Eshkol (24) implies that the prohibition is only m’d’Rabanan.
There is a machlokes Rishonim whether the kedusha of a shul is m’d’Oraisa or m’d’Rabanan. The Ran and Ramban in Megillah state that it is only m’d’Rabanan. The Yiraiyim (409) states that it is m’d’Oraisa. There is a dispute as to what the opinion of the Rambam is. The Avnei Nezer (Orach Chaim 35) and the Toras Chesed (Orach Chaim 4:7) believe that the Rambam is of the opinion that a beis knesses and beis midrash have kedusha m’d’Oraisa. Perhaps this is the underlying dispute whether it is prohibited to destroy any part of a shul
The Minchas Chinuch (mitzvah 337:18 and 254:5) asks the following question: the Rambam states that it is only prohibited to destroy parts of the azara of the Beis Hamikdash. M’d’Oraisai, this does not apply to the rest of Har Habayis. How then can a shul be more stringent than Har Habayis that has more kedusha? One may not enter Har Habayis with his moneybag, yet he may enter a shul with it. How can the Rambam hold that it is forbidden m’d’Oraisa to destroy a shul and prohibit only m’d’Rabanan to destroy parts of Har Habayis?
Based on this question several Acharonim (Ein Yitzchak (Orach Chaim 5:19) Chelkas Yoav (Orach Chaim 4)) say that despite the implicit language of the Rambam, he actually holds that it is prohibited only m’d’Rabanan to destroy a shul. However, as we have quoted above, many Acharonim maintain that the Rambam’s opinion is that destroying a shul is prohibited m’d’Oraisa. This question then falls on their view.
Perhaps a careful reading of the pesukim in the parsha will shed light on this dilemma. The Torah writes that when we get to Eretz Yisrael we should destroy all of the places of idol worship. The pasuk continues, that we should destroy their altars, decimate their pillars, and burn their trees that they have worshiped. You should also cut down their carved images, and obliterate their names from those places. Then the Torah says that we should not do this to Hashem your God. We can imply that the prohibition not to destroy sacred things such as the Beis Hamikdash and possibly a beis knesses is the polar opposite of the commandment to destroy the idol-worshiped places.