At a Hupa, before the bride and groom perform Erusin ("betrothal"), the officiating Rabbi recites the Beracha known as Birkat Erusin ("Baruch Ata Hashem…Asher Kideshanu Be’misvotav Ve’sivanu Al Ha’arayot Ve’asar Lanu Et Ha’arusot…"). Different views exist among the Halachic authorities in classifying this Beracha. The Ben Ish Hai (Rav Yosef Haim of Baghdad, 1833-1909), interestingly enough, defined Birkat Erusin as a "Birkat Ha’nehenin" – a Beracha recited before deriving benefit from God’s world. Just as we must recite a Beracha before eating and deriving benefit from the earth, the Ben Ish Hai writes, similarly, a groom must recite Beracha before deriving benefit from the bride. According to the Ben Ish Hai, then, Birkat Erusin is under the same category as "She’hakol" and "Boreh Peri Ha’etz."
Many scholars, however, questioned this theory, noting that even after Birkat Erusin, the bride remains forbidden to the groom. Relations become permissible only after Nisu’in, which is the second stage of the marriage process, after Erusin. It therefore seems difficult to classify Birkat Erusin as a "Birkat Ha’nehenin," if it does not render the bride permissible to the groom.
The Rosh (Rabbenu Asher Ben Yehiel, Germany-Spain, c. 1250-1327) wrote that Birkat Erusin falls under the category of "Birkot He’shebah," Berachot that we recite to give praise to the Almighty for various phenomena. It is similar to the Beracha of "Shehehiyanu" recited over joyous experiences, and other Berachot that we recite when certain phenomena occur to give praise to Hashem for bringing about those events. At the time of a wedding, we give praise and thanks to Hashem for creating this wondrous concept of a man and woman getting married to one another.
The third view is that of the Rambam (Rabbi Moshe Maimonides, Spain-Egypt, 1135-1204), who classified Birkat Erusin as a "Birkat Ha’misva" – a Beracha recited over a Misva. Just as we recite a Beracha before wearing a Tallit, before wearing Tefillin, before eating in the Sukka and before taking a Lulab, one must recite a Beracha before performing the Misva of getting married, which is part of the Misva of "Peru U’rbu" (procreation). Indeed, the text of the Misva strongly resembles the standard text of a Birkat Ha’misva ("Baruch Ata Hashem…Asher Kideshanu Be’misvotav Ve’sivanu…").
We follow the Rambam’s position this regard, and this ruling yields important Halachic ramifications. Specifically, since this Beracha is a Birkat Ha’misva, recited over the Misva of getting married, it is the Hatan who should, in principle, recite this Beracha. As he is the one performing the Misva, he is the one who should recite the Beracha over the Misva. The reason the Rabbi recites Birkat Erusin is to avoid causing shame to grooms who are not proficient in the text of this Beracha. Many grooms are not familiar with Birkat Erusin, and therefore in order not to cause them embarrassment under the Hupa, it became customary for the Rabbi to recite the Beracha on the groom’s behalf. Therefore, it is incumbent upon the Rabbi to instruct the Hatan to listen carefully to the Beracha and have in mind to fulfill his obligation through the Rabbi’s recitation. He must answer "Amen" after the Rabbi’s recitation, and he should not respond "Baruch Hu U’baruch Shemo" in the middle of the recitation. Hacham Ovadia Yosef writes that the Rabbi should instruct the bride, too, to listen carefully to the Beracha, even though, strictly speaking, he recites the Beracha specifically on behalf of the groom, as it is the groom’s requirement to recite the Beracha.
The Birkat Erusin is preceded by the Beracha of "Boreh Peri Ha’gefen" over a cup of wine. According to the strict Halacha, the Birkat Erusin does not require a cup of wine; wine is required only for the Berachot of the Nisu’in recited at the end of the Hupa ceremony. As such, the Beracha over the wine is not actually a part of the Birkat Erusin, and is therefore simply an ordinary Birkat Ha’nehenin over wine. Of course, a person cannot recite an ordinary Birkat Ha’nehenin for somebody else without eating or drinking himself. Therefore, the Rabbi, who recites the Beracha of "Boreh Peri Ha’gefen," must drink some of the wine. The problem, however, arises that if he drinks from the cup before giving it to the bride and groom to drink, he can no longer give it to them, because the cup will be "Pagum" (already used). It is therefore customary that the Rabbi, immediately after concluding the recitation of Birkat Erusin, slightly tilts the cup of wine so that a small amount of wine spills on his finger. Then, after he gives the cup to the bride, he sips the wine from his finger, so that his Beracha of "Boreh Peri Ha’gefen" does not become a "Beracha Le’batala" (a "wasted" Beracha). Indeed, this was the practice of Hacham Baruch Ben Haim z"l.
Summary: Strictly speaking, it is the groom who should recite the Birkat Erusin under the Hupa, as he is the one performing the Misva of getting married. In practice, however, the Rabbi recites the Beracha on his behalf, and he must listen attentively to the Rabbi’s recitation, having in mind to fulfill his obligation, and then answer "Amen." Immediately after the recitation, the Rabbi should tilt the cup so that a few drops of wine fall on his finger, and he should then sip the wine from his finger after handing the cup to the bride.
