1)

a) I suggest that the reason why Rashi mentions Hachnasas Kallah is that this is a specially big Mitzvah. A source for this is the Tur (Even ha'Ezer 65) who writes, "It is a great Mitzvah to make the Chasan and the Kallah happy." The Tur does not write in many places that something is a great Mitzvah.

This sometimes has Halachic ramifications. See the Rema in Hilchos Shabbos (Orach Chayim 338:2) who rules that one may ask a Nochri to make a musical instrument on Shabbos in order to make the Chasan and Kallah happy. The Magen Avraham (#4) wonders why the Rema permits asking the Nochri to do a Melachah d'Oraisa on Shabbos for a Mitzvah when, generally, it is permitted only to ask a Nochri to do a Melachah d'Rabanan on Shabbos for the sake of a Mitzvah. The Magen Avraham implies with his answer that Simchas Chasan v'Kallah is greater than other Mitzvos. The Pri Megadim there states this explicilty, that Kavod Chasan is "an extremely great Mitzvah."

b) Every Mitzvah is much greater when it is done with Simchah. Rabeinu Yonah (Sha'arei Teshuvah, Sha'ar 4:9) writes that one of the reasons for why we have a meal before Yom Kippur is that we make a Se'udah on every Yom Tov for the joy of the Mitzvah. The reward for the Simchah of a Mitzvah is very great and exalted.

c) Joy is a very important part of the Mitzvah of Esrog and Lulav. In the context of the Mitzvah of Esrog and Lulav, the Torah says, "And you shall be happy before Hash-m for seven days" (Vayikra 23:40).

(It is very appropriate that we are discussing this now, as we prepare for the Simchah of Lag ba'Omer, a great day to make a wedding!)

2)

a) It is not only a Navi who can bring Hashra'as ha'Shechinah. Whenever we learn Torah we receive the Shechinah. The Mishnah in Pirkei Avos (3:6) says that when then people sit and learn Torah the Shechinah rests upon them. Even when one person learns Torah, Hash-m comes to him to bless him.

b) When we put on Tefilin every day, the Shechinah rests upon us (see Rabeinu Bachye, Shemos 25:9: "The Shechinah rests upon him with the Mitzvah of Tefilin on his head and his arm, correspondong to the brain and the heart").

3) We saw above that Rabeinu Yonah teaches that we reach Simchah through a Se'udah of a Mitzvah. In addition, I found that the Midrash Talpiyos says that since we know that our table nowadays gives us a Kaparah in the same way that the Mizbe'ach did in the Beis ha'Mikdash, this means that the Shechinah rests on our table where we celebrate our Se'udos of Mitzvah.

4) I looked up what the Mefarshim say about why Rashi gives Hachnasas Kallah as an example of Simchah Shel Mitzvah. I found that the Torah Temimah on Koheles 2:2 (note 7) writes that he does not understand why Rashi does not explain that this Simchah means the joy that comes from doing any Mitzvah or good deed. The Torah Temimah appears to be concerned with why Rashi singled out any Mitzvah, if doing anything good according to the Torah makes a person happy if he does it in the right way.

5) Rav Moshe Feinstein zt'l, in Dibros Moshe (Shabbos 26:80), writes that it seems that Simchah Shel Mitzvah refers to the Simchah from Mitzvos that we are commanded to do with joy. An example of these is Hachnasas Kallah, as Rashi writes. Another example is the Simchas Beis ha'Sho'evah that we have on Sukos, or the Mitzvah of joy that we have on every Yom Tov. The Dibros Moshe writes that the Rambam (Hilchos Lulav 8:15) also explains a similar idea. The Rambam writes, "The Simchah that a person rejoices when he does Mitzvos, and when he loves Hash-m who commanded them, is a great work." The Dibros Moshe writes that "Hash-m who commanded them" refers to the Mitzvos on which Hash-m commanded us to rejoice. The Dibros Moshe learns that some Mitzvos are special because we are told specificially to be happy with them.

6) I think that what I wrote earlier can still help us understand the matter. According to the Dibros Moshe, Rashi looked for a Mitzvah which we are commanded to do with Simchah. But why did Rashi not choose the Mitzvah of Simchas Beis ha'Sho'evah or the Mitzvah of being happy on Yom Tov? The answer is that Hachnasas Kallah is the greatest of the Mitzvos which we are commanded to do with Simchah. As the Pri Megadim puts it, it is an extremely great Mitzvah, so this is why Rashi singled it out.

Kol Tuv,

Dovid Bloom

As I look again at these questions, I see that I have not really covered all of the important ideas raised here.

1) To further address the question, "What Mitzvah is it to bring on Hashra'as ha'Shechinah," let us phrase this slightly differently: "Which one of the 613 Mitzvos is it to bring on Hashra'as Shechinah?"

We may conjecture that this is included in the Mitzvah of, "And you shall walk in His ways" (Devarim 28:9). The Sefer ha'Chinuch writes (Mitzvah 611) that we have a Mitzvah to conduct ourselves in similar ways to those of Hashem. It seems to me that if we are walking in the way of Hashem, this means we are bringing the Shechinah upon ourselves, because we are emulating Hashem.

2) It is also important to mention that the Maharsha writes here (DH Zu) that "the Mitzvah causes the Shechinah to rest on the person who does it; and it must be done joyfully."

We learn from the Maharsha that any Mitzvah can achieve Hashra'as ha'Shechinah. No doubt, Rashi gave the example of Hachnasas Kallah because this is easier to do joyously, so it is easier to bring the Shechinah that way, but in fact every Mitzvah has the potential to induce the Shechinah if done in the right way.

Additional source:

I asked a Talmid Chacham which of the 613 Mitzvos of the Torah tell us that it is a Mitzvah to bring the Shechinah upon oneself, and he answered that possibly this is included in the Mitzvah of "uVo Tidbak"; "And you shall cleave to Him".

Dovid Bloom

Kol Tuv,

Dovid Bloom