The Torah in Parashat Shoftim introduces the prohibition against erecting a matzeiva (“monument” – 16:22). Rashi explains this prohibition as referring to an altar made of just one stone, as opposed to altars made of numerous stones. Avraham, Yitzchak and Yaakov erected and sacrificed on altars made of one stone, Rashi writes, but this had since become a fixture of pagan ritual, and the Torah therefore prohibited erecting or using such altars.
The Rambam, however, explains this prohibition much differently. He writes in Hilkhot Avodat Kokhavim (6:6) that the Torah here forbids “a structure near which everybody assembles, even to serve God.” Such structures are forbidden, the Rambam writes, because this type of gathering was common among the ancient pagans. According to the Rambam, then, this prohibition refers to any structure used for religious gatherings, regardless of how many stones it is made from, and whether or not it is used for sacrifices.
A number of scholars, including Rav Kook (Tov Ro’i) and the Maharil Diskin (Parashat Shoftim), understood the Rambam as drawing a distinction between gatherings held inside buildings, and gatherings held alongside structures. Synagogues, quite obviously, are allowed (and, of course, required) because the religious gatherings are held inside them. A matzeiva which the Torah forbids is a structure around which people assemble, as opposed to a structure within which people assemble. (This point is also made by Rav Kook’s son, Rav Tzvi Yehuda Kook, in Meorot HaRav Tzvi Yehuda, vol. 1, p. 356.)
An interesting contemporary halakhic question that arises in this regard relates to the building of memorial monuments where gatherings are often held in honor of a deceased person or deceased persons. At first glance, it would appear that according to the Rambam’s view, such structures meet the definition of “matzeiva” and should thus be forbidden. Indeed, Rav Moshe Sternbuch, in his Ta’am Va-da’at (Parashat Shoftim) and in his Da’at U-machashava (Hilkhot Avodat Kokhavim), strictly forbids such monuments, asserting that they constitute an “issur chamur” (“grave prohibition”), and that this practice has its origins in other faiths and may not be observed according to Torah law.
Others, however, disagree. Rav Yehuda Leib Tsirelson Hy”d, in his Ma’arkhei Leiv (42), was asked by the Jewish community in Carlsberg about the permissibility of erecting a monument in memory of their fallen youth, and he ruled that this was allowed. He notes in his responsum that, first and foremost, several Rishonim – in addition to Rashi – disagree with the Rambam’s definition of “matzeiva,” and maintain that a structure is included under this prohibition only if it is made for sacrificial worship. According to their position, a memorial structure, which serves no religious purpose, is certainly allowed. Moreover, Rav Tsirelson writes, even the Rambam would forbid a structure only if it serves some form of religious purpose, which is not the case with monuments erected to memorialize the deceased.
Rav Tsirelson briefly adds also another factor, namely, that no nation today uses monuments for religious practices as was done by the ancient pagans. Rav Yitzchak Weiss, in a responsum on the subject printed in his Minchat Yitzchak (1:29), understands Rav Tsirelson’s comment to mean that the prohibition against erecting a matzeiva is inherently contingent upon the concern that it might appear or be misconstrued as a site of pagan worship, such that this law does not apply when monuments are not used for foreign worship. Rav Weiss suggests drawing support for this theory from the fact that the Shulchan Arukh makes no mention of this prohibition (an omission noted also by Rav Sternbuch, in the sources cited earlier). The Shulchan Arukh evidently felt that this law does not apply nowadays, perhaps for the reason indicated by Rav Tsirelson. Rav Weiss immediately adds, however, that this consideration alone would not be sufficient to permit monuments, as the Sefer Ha-chinukh (493) writes explicitly that the prohibition against erecting a “matzeiva” applies in all historical periods.
Regardless, Rav Weiss concurs with Rav Tsirelson’s ruling and concludes that erecting memorial monuments is, in fact, permissible.