1) HALACHAH: ON WHAT DAY OF THE WEEK SHOULD ONE GET MARRIED
OPINIONS: The Gemara discusses at length the Mishnah (2a) which mentions the day of the week on which one should marry a Besulah or an Almanah. In practice, on which day should one marry a Besulah?
(a) IKRUREI DA'ATA. The primary reason for why the Mishnah says that a man who marries a Besulah should get married on Wednesday is because of "Ikrurei Da'ata"; if a man finds that his wife is not a Besulah, the Rabanan want him to come to Beis Din immediately so that he does not "cool off" and decide that he prefers to live with his wife (to whom he is prohibited if she indeed was unfaithful while she was an Arusah). By getting married on Wednesday, if he finds that his wife is not a Besulah he will come to Beis Din immediately on Thursday morning, when Beis Din convenes. (The other two reasons for getting married on Wednesday (5a) -- to receive the Berachah given to fish and because of "Shakdu," can be circumvented: the reason of "Berachah" is merely a suggestion and not an obligation, and "Shakdu" can be accomplished by preparing for three days in advance of any day of the week on which one wishes to get married (end of 3a).)
The reason of "Ikrurei Da'ata" should not apply nowadays. The Gemara (3a) says that when Beis Din convenes every day, the marriage may be held on any day, because the man always has the opportunity to go to Beis Din immediately.
However, TOSFOS (3a, DH Iy Ika) points out that this does reasoning does not seem to suffice to permit a marriage to be held on Friday. If one performs Be'ilas Mitzvah on Friday night, he will not find a Beis Din on Shabbos. (Even if Beis Din convenes every other day of the week, it certainly does not convene on Shabbos.)
The Rishonim, however, give a number of reasons to permit marriage even on Friday:
1. Nowadays there is no set day on which Beis Din convenes. Instead, whenever a person has the need for a court, he gathers together three Talmidei Chachamim and presents his claims before them. A person may do that even on Shabbos if he needs to file a complaint about his newly married wife's lack of Besulim.
2. Perhaps today the enactment of "Ikrurei Da'ata" does not apply due to the reasoning of Rashi earlier (2a, DH b'Sheni). Rashi writes that the purpose of reporting in court that one's wife was not found to be a Besulah is in order to publicize the claim in case there are witnesses who can come to testify how she became a Be'ulah. This does not apply nowadays. Since there are no official courts for such matters and family disputes do not attract onlookers and crowds, the word does not get out.
However, this reason applies only for the wife of a Yisrael, in which case it is necessary for witnesses to come to testify about the woman's status. For the wife of a Kohen or for a wife who was betrothed when she was less then three years old, it is still imperative that he come to Beis Din, because in those cases his wife is prohibited to him out of doubt, even without witnesses. Why, then, should a Kohen be permitted nowadays to get married on any day other than Wednesday?
The answer might be that according to Rashi, the Rabanan did not institute that a man should get married on Wednesday because he might be a Kohen and need to go to Beis Din the next day. They instituted the Takanah in the first place only because it benefits everyone to some degree (see Tosfos 2a, DH she'Im). Once it no longer benefits everyone, the Takanah no longer applies at all, even for a Kohen.
3. The RAN (1b of the pages of the Rif) writes that nowadays Kidushin and Nisu'in are done together, Nisu'in immediately following Kidushin (with no delay between the two). As such, it is not possible for the woman to commit adultery as an Arusah -- there is no time between the Kidushin and Nisu'in during which she can be unfaithful without her Chasan seeing her. Since there is no fear that she is prohibited to him, there is no need for him to come to Beis Din if he finds that she is not a Besulah, and thus he may get married on any day of the week. (The Gemara later (12a) presents a similar logic, "she'Kidesh u'Ba'al l'Altar.")
(b) SHEMA YISHCHOT BEN OF. Another reason to prohibit marrying on certain days of the week is the Gezeirah which prohibits Be'ilas Mitzvah on Friday night and on Motza'i Shabbos. That is, although the Gemara here concludes that one is permitted to perform the first Be'ilah on Shabbos, the Gemara earlier (4a) cites a Beraisa that states that one may not perform the first Be'ilah on Friday night or Shabbos because of the reason of "Shema Yish'chot Ben Of" -- one might slaughter a bird on Shabbos. It was customary to conduct a festive Se'udah following the Be'ilas Mitzvah, and the Rabanan feared that if the Be'ilas Mitzvah would be performed on Shabbos, the preparation for the Se'udah might take place on Shabbos. Accordingly, getting married on Friday should be prohibited nowadays because of that Gezeirah.
The Rishonim discuss this question and some maintain that the Gezeirah nevertheless does not prohibit marrying on Friday:
1. TOSFOS (7a, DH v'Hilchasa), the RAN, and the ROSH point out that the Gemara rules that the first Be'ilah is permitted on Shabbos, and the Gemara makes no mention of the Gezeirah lest one slaughter a bird on Shabbos. It seems that the Gemara rejects the earlier Beraisa that maintains that the Be'ilas Mitzvah may not be done on Shabbos because of the Gezeirah lest one slaughter a bird on Shabbos.
The RIF does not mention the reason of "perhaps one might slaughter a young bird on Shabbos" at all. The RAMAH quoted by the SHITAH MEKUBETZES (5a, DH Hashta) writes that according to the Rif, the Gemara rejects the Beraisa's reason for prohibiting Be'ilas Mitzvah on Friday night, and certainly it rejects that reasoning with regard to Motza'i Shabbos (since he is not actually involved with the Se'udah on Shabbos).
The RAMBAN (5a) adds another reason for why there is no concern that one might slaughter a bird on Shabbos: Nowadays it is not the practice to make a Se'udah for the Be'ilas Mitzvah, and therefore there is no fear that one might slaughter on Shabbos.
2. The TALMIDEI RABEINU YONAH cited by the SHITAH MEKUBETZES (5a, ibid.) argue that this logic only permits marrying on Erev Shabbos but not on Motza'i Shabbos. They explain that it is possible that the Gezeirah which prohibits getting married on Friday because of the fear that one might slaughter a bird on Shabbos will apply to Motza'i Shabbos because one prepares for a nighttime Se'udah during the preceding day. Hence, one prepares on Friday for the Se'udah conducted on Friday night, and thus there is no fear that one will slaughter on Shabbos.
However, for the Se'udah conducted on Motza'i Shabbos one does not prepare entirely on Friday, because he assumes that he will have time to finish the preparations on Motza'i Shabbos. Therefore, there is a concern that he might slaughter on Shabbos when he sees that there will not be enough time to prepare on Motza'i Shabbos.
3. However, the RAMBAM (Hilchos Ishus 10:14) rules that a person "may not get married on Friday or on Sunday, because one might desecrate Shabbos by preparing for the Se'udah."
Although the Gemara here says that one is permitted to perform Be'ilas Mitzvah on Shabbos, the RAN (2a of the pages of the Rif) explains that there is a difference between performing Be'ilas Mitzvah on Shabbos and getting married on Shabbos. That is, the Rambam maintains that the Isur of Be'ilah Rishonah on Friday or Sunday lest one slaughter a bird on Shabbos is a prohibition of getting married on Friday or Sunday, and not a prohibition of Be'ilas Mitzvah on those days. The Se'udah for which one might prepare on Shabbos is the Se'udas Nisu'in.
It is true that TOSFOS (5b, DH Mahu) presents a similar logic to explain why the allowance to perform the first Be'ilah on Friday night is not contradicted by the Mishnah. The Mishnah discusses the day on which the wedding should be held, but it does not require that the first Be'ilah be performed on the same day. However, the Beraisa (4a) which teaches the Gezeirah of "Shema Yishchot Ben Of" says that "one should not do Be'ilah on Friday night and Motza'i Shabbos." How, then, can the Rambam suggest that the Beraisa is teaching a Halachah about the marriage and not about the Be'ilah?
The answer is that the Rambam apparently understands that the Beraisa says that "one should not do Be'ilah" simply because the Beraisa until now was discussing Be'ilah Rishonah. The Rambam does not want to explain the Beraisa literally because he maintains that there is no source for making a Se'udah on the occasion of the first Be'ilah (on the contrary, doing so would seem to be a lack of Tzeni'us).
HALACHAH: The SHULCHAN ARUCH (EH 64:3) writes that if Beis Din convenes on Mondays and Thursdays, then a man is required to get married on Wednesday. If Beis Din does not convene on those days, then one may get married on any day of the week as long as he busies himself with preparing for the Se'udah three days in advance. As far as the concern for "Ikrurei Da'ata," Friday is considered the same as any other day.
With regard to the Isur of "Shema Yish'chot Ben Of," the Shulchan Aruch cites the view of the Rambam that one should not get married on Friday or Sunday, and he also cites the view of Tosfos and the other Rishonim who permit one to get married on Friday or Sunday.
The Shulchan Aruch adds that it has become customary to get married on Friday. This is based on the RA'AVYAH (quoted by the MORDECHAI here and by the HAGAHOS MAIMONIYOS in Hilchos Ishus 10:50) who writes that it became customary to get married on Friday to benefit the poor people who could not afford to make a separate Se'udah for both their wedding and for Shabbos, and by getting married on Friday they were able to combine both Se'udos into one.
The Ra'avyah adds that nowadays it is customary that even an Almanah gets married on Friday, even though this will mean that the husband will not have his three-day vacation with his new wife. The Chachamim of the past generations determined that it is more beneficial to marry on Friday for the sake of the poor people than to ensure that the three-day vacation takes place. The Shulchan Aruch, however, writes that an Almanah should get married on Thursday, as the Mishnah says.
The PNEI YEHOSHUA (in Kuntrus Acharon) points out that l'Chatchilah a person still should get married, if possible, on Wednesday or Thursday because of the Berachah given to fish, since one should not take lightly the Berachah mentioned by the Gemara.

7b----------------------------------------7b

2) "BIRKAS ERUSIN" -- THE BLESSING FOR KIDUSHIN
QUESTION: The Gemara describes the Berachah of Birkas Erusin recited at the time the Erusin is performed. The Berachah mentions that Hash-m "prohibited us to [marry] the Arayos," and that "He prohibited us to the Arusos," and "permitted us to Nesu'os" when they become our full-fledged wives when the Chupah is performed.
Why does the Berachah make mention of the prohibition of Arayos? The Berachah was instituted for the Mitzvah of Kidushin, and not for the prohibition of Arayos!
Moreover, why does the Berachah mention the Chupah (the procedure of Nisu'in), when the Berachah was instituted for the Kidushin?
Also, why is the Chupah mentioned in the Berachah before the Kidushin ("Chupah v'Kidushin"), when, in practice, the Kidushin precedes the Chupah?
ANSWERS:
(a) RASHI seems to learn that Birkas Erusin is not a Berachah on the Mitzvah of Erusin, but rather it is a Berachah on the Mitzvah d'Rabanan of "Perishah," separating ourselves from unmarried women. Although a Berachah is usually not recited for a Mitzvah that involves refraining from an action, perhaps the Chachamim saw fit to institute a Berachah for separating from an Arusah because this "inaction" is more evident than most actions and thus it warrants a Berachah. After the betrothal, everyone expects the woman to move in with her husband, and yet they continue to stay apart. Therefore, at the time that they do Kidushin it is appropriate to recite a Berachah on this conspicuous inaction of separation that they are practicing.
Rashi explains that the Isur of Arayos mentioned in the Berachah refer to the Isur of living with a Penuyah, an unmarried woman. The reason why the Chupah is mentioned in the Berachah is to express that until the Chupah is performed, the Penuyah is forbidden to him. The reason why the Chupah is mentioned before the Kidushin apparently is that the allowance to live with a woman comes at the time of the Chupah. The Berachah, which focuses on the Heter to be with one's wife only after the Chupah, mentions the Kidushin only as a prerequisite to the Chupah.
(b) The ROSH (1:12) explains that no Mitzvah d'Oraisa is fulfilled when one performs Erusin. The Mitzvah is not necessarily to get married, but rather to have children -- "Piryah v'Rivyah." The Mitzvah of having children could be fulfilled with a Pilegesh without Kidushin. Kidushin is merely an option which the Torah gives if a person wants to have a wife and fulfill the Mitzvah of Piryah v'Rivyah with her.
In this respect, this Mitzvah seems similar to the Mitzvah of Shechitah, for which one also recites a Berachah even though there is no obligation to perform the Mitzvah of Shechitah (only if one wants to eat meat must he first perform Shechitah). However, Shechitah differs from Kidushin in that there is no other way to eat meat without doing Shechitah, and thus Shechitah is a necessity for one who wants to eat meat. In contrast, one who wants to have children does not necessarily have to perform Kidushin with a woman to do so, but instead can take a Pilegesh and have children with her. The Rosh gives additional reasons why the Chachamim did not institute a Birkas ha'Mitzvah for Erusin.
What, then, is the purpose of the Berachah according to the Rosh? It is a Berachah of praise to Hash-m for granting holiness, Kedushah, to the Jewish people. We praise Hash-m for giving us the laws of Kidushin, including the laws that describe with which women Kidushin takes effect and with which women it does not take effect. The concept of Kidushin does not exist for the people of any other nation. The institution of Kidushin give the Jewish people a degree of holiness which no other people has. For this reason, the prohibition of Arayos is mentioned in the Berachah -- to praise Hash-m for giving Kedushah to the Jewish people through the laws of Arayos.
The reason why the Berachah mentions that an Arusah becomes permitted at the Chupah is so that people should not mistakenly think that the purpose of the Berachah of Kidushin is to permit the Arusah to her husband. The Berachah specifically mentions that she becomes permitted to him only at the Chupah. This also explains why the Chupah is mentioned before the Kidushin. The main point of the Berachah is that only at the time of the Chupah, which follows the Kidushin, does the woman become permitted to her husband. (This last point is similar to the approach of Rashi in (a) above.)
(c) The RAMBAM (Hilchos Ishus 2:23) rules that Birkas Erusin is a Birkas ha'Mitzvah for the Mitzvah of Kidushin. Like any other Berachah recited for the performance of a Mitzvah, it must be recited before the Mitzvah of Kidushin is performed. The RA'AVAD there and the RAMBAN and RASHBA here seem to agree that the Berachah is a Birkas ha'Mitzvah.
The Rambam and Rashba apparently follow their opinion as expressed elsewhere. The Rambam (Hilchos Melachim 4:4; see also Ramban, Bereishis 25:6) and Rashba (Teshuvah 4:314) write that normally one is not permitted to take a Pilegesh, and thus there is no way to fulfill the Mitzvah of Piryah v'Rivyah without marrying a woman with Kidushin. Consequently, Kidushin is a Mitzvah just like Shechitah, which warrants a Berachah.
The Rashba writes that there is a different reason for why a Berachah is not recited for the Mitzvah of Kidushin even though it is necessary for the Mitzvah of Piryah v'Rivyah. Since Kidushin is only the beginning of the Mitzvah and does not complete it, it does not warrant a Birkas ha'Mitzvah.
However, the Rishonim quote the Yerushalmi which clearly states that a Birkas ha'Mitzvah is recited for Kidushin. (The Yerushalmi says that the Berachah on Kidushei Be'ilah is said after the Kidushin and not before.) It is clear from the Yerushalmi that Kidushin is considered a separate Mitzvah. This is the view of RABEINU YECHIEL of Paris as quoted by the RITVA, who says that since Kidushin is a distinct Mitzvah apart from Nisu'in, as it accomplishes an entirely different purpose than Nisu'in (it creates an Isur l'Olam, while the Nisu'in gives the husband a certain degree of Kinyan over the woman), it warrants its own Berachah. (The Rashba maintains that the Bavli must be arguing with the Yerushalmi since it does not mention that Berachah.)
It is not clear from the Yerushalmi exactly what the text of the Birkas Erusin should be. The Yerushalmi, when it mentions the Berachah, might be referring to the Berachah mentioned in the Gemara here (as the Ramban implies), but it also might be referring to a separate Berachah entirely (such as "... Asher Kidshanu b'Mitzvosav v'Tzivanu Al Mitzvas Kidushin"), as Rabeinu Yechiel seems to interpret it.
According to this approach (that Birkas Erusin is a Berachah on the Mitzvah of Kidushin), it is not clear why the Isur of Arayos and the Chupah are mentioned in the Berachah. Perhaps these Rishonim agree with the Rosh (in (b) above) who says that the point of the Berachah is to remind people that Erusin does not permit the Arusah to her husband.
HALACHAH: The SHULCHAN ARUCH (EH 34:1) writes that Birkas Erusin should be recited before the act of Kidushin, implying that it is a Birkas ha'Mitzvah (see Beis Shmuel #4 and Chelkas Mechokek #3 there). (The Poskim do not mention the Berachah of "Al Mitzvas Kidushin" which Rabeinu Yechiel mentions, but some do mention a special Berachah for the Be'ilas Mitzvah which is recorded by the Ge'onim, and they add that it should be said without "Shem u'Malchus.")
3) "PANIM CHADASHOS"
OPINIONS: The Gemara says that all of the seven Berachos of "Birkas Chasanim" are recited on each of the seven days after the wedding only when "Panim Chadashos" are present. When no "Panim Chadashos" are present, only one Berachah ("Asher Bara") is recited (along with "Borei Pri ha'Gafen").
Why is it necessary to have "Panim Chadashos" in order to recite all seven Berachos?
(a) TOSFOS (DH v'Hu) says that "Panim Chadashos" increase and enhance the Simchah. The seven Berachos are recited for the added Simchah provided by the "Panim Chadashos."
(b) The RAMBAM (Hilchos Berachos 10:2) writes that the seven Berachos are repeated only when there are "Panim Chadashos" present because the new person present did not yet hear the Berachos, and since he is now participating in the Simchah he has an obligation to say (or hear) the Berachos for the Simchah. Therefore, the seven Berachos are recited again because of the new person's obligation to hear them.
The Rishonim and Acharonim point out that there are a number of practical differences between these two ways of understanding the role of "Panim Chadashos."
1. Tosfos writes, based on a Midrash, that on Shabbos it is not necessary to have "Panim Chadashos" because Shabbos itself is called "Panim Chadashos." Tosfos explains that this means that since Shabbos itself causes extra Simchah, the Sheva Berachos may be recited even when there are no new persons present.
In contrast, according to the Rambam, Shabbos alone is not a reason to say the seven Berachos because Shabbos is not a person and has no obligation to recite Berachos. (The RITVA, who requires a person obligated in Berachos for "Panim Chadashos," suggests another reason for the custom not to require "Panim Chadashos" at the Sheva Berachos of Shabbos.)
Similarly, according to Tosfos, if the presence of a woman or a child provides more Simchah to the wedding party, the seven Berachos would be recited even though a woman and a child are not obligated to recite the Berachos themselves. According to the Rambam a woman and a child do not constitute "Panim Chadashos" since they have no obligation to recite or hear the Berachos. This indeed is the ruling of the RITVA. (The Ritva seems to represent a third opinion, which requires both a person that increases the joy of the occasion and a person who is required to make a Berachah.)
2. The RAMACH and the ROSH write that even if all of the people at the Se'udas Nisu'in attended the Chupah and heard the seven Berachos, they still may recite the seven Berachos at the Se'udah because there is a separate obligation for reciting the seven Berachos at the Se'udah.
The Rambam and Ritva write, however, that the seven Berachos may be recited only if someone is present who did not hear the Berachos at all, including the Berachos at the Chupah. The Ritva apparently follows his opinion in this matter as mentioned above.
3. If a person was not present at the wedding during the meal but only at the recitation of the Sheva Berachos, the Ritva considers him as valid "Panim Chadashos" (and the Rambam presumably would agree). Tosfos, in contrast, might not consider him as valid "Panim Chadashos." (The opposite would be true for a person who was at the wedding during the meal but did not remain for the Sheva Berachos.)