Halakhic Positions of Rav Joseph B. Soloveitchik
by R. Aharon Ziegler
The common practice is that the Chatan [groom] breaks a glass at a wedding. Many assume that this is to remind all those in attendance of the destruction of the Beit HaMikdash, as is mentioned in the Rama to Orach Chaim [Siman 560]. This idea is based on the pasuk in Tehilim [137:6] which encourages all to always make mention of Yerushalayim at all times, even on the joyous occasion of a wedding. In the Gemara Berachot [31a], which is the source of the custom, the practice is recorded in a somewhat different context; even when one rejoices at any occasion, the cheerfulness should always be toned down a bit, lest it lead to levity.
Rav Soloveitchik thought that the breaking of the glass has another meaning; namely-that it is also reminiscent of The Revelation of Mt. Sinai, ma’amad Har Sinai. The Midrash [Tanchuma to parshat Ki Tissa] points out that because the first Luchot were given with great publicity and fanfare, this had a negative effect, and caused them to be broken. The second set of Luchot was given privately, [betzinah] and therefore it lasted. Through this contrast, the Torah teaches us the lesson of tzniut, of always leading a private life. HaShem is described by the Yeshaya [45:15] as a “Kel Mistater”, as one who is in hiding. We were all created “in his image” and commanded to preserve that “tzelem Elokim” by leading our lives in the “ways of G-d”. We break the glass at the wedding to impart to the young couple that they must lead a life of tzni’ut; otherwise their marriage may suffer, just as the first set of Luchot was smashed.
The Tashbetz  writes, “all of the customs of the Jewish marriage ceremony have their sources in mattan Torah.” The Maharam of Rothenberg is quoted in  as having translated the expression “Harei at Mekudeshet li k’dat Moshe veYisrael”, as, “I hereby marry you, just as the Jewish people are married to the Torah. “We are married to the Torah, and thereby, married to G-d”. This supports the contentions of the Rav.