1) HALACHAH: GETTING MARRIED DURING "AVEILUS"
OPINIONS: The Gemara says that if a Chasan and Kalah were about to get married and all of the preparations for the wedding had been made, and then the father of the Chasan or mother of the Kalah passed away, the body is moved to a different room, the Chupah is performed, they do Be'ilas Mitzvah, and then they bury the dead. After the burial, they observe seven days of Mishteh (celebration) followed by seven days of Aveilus.
The Gemara says that this procedure applies only if it is specifically the father of the Chasan or the mother of the Kalah who died, as opposed to other relatives. In addition, it applies only if the food that was prepared for the wedding will spoil if the wedding is not performed immediately.
What is the procedure if a different relative of the Chasan or Kalah dies, or if the food will not spoil if the wedding is postponed?
(a) The RIF, as explained by the ROSH (1:6), writes that if the food will not spoil, or if it has not yet been prepared, the dead body still is removed to a different room and the Chupah is performed and Be'ilas Mitzvah is done, just as in the case of the Gemara. The difference is that after burying the dead, the seven days of Aveilus are observed first, and then the seven days of Mishteh are observed. The Rosh cites the MAHARITZ GE'AS who rules that the same applies when a different relative (other than the father of the Chasan or the mother of the Kalah) passes away; the Chupah is performed and Be'ilas Mitzvah is done, but the seven days of Aveilus are observed first, followed by the seven days of Mishteh.
The source for their ruling appears to be the Gemara (at the end of 4b) that states that allowing the Chasan and Kalah to get married and do Be'ilas Mitzvah is not a leniency instituted by the Rabanan in the laws of Aveilus, because the Aveilus does not start until after the burial. Rather, the leniency is that the seven days of Mishteh precede the seven days of Aveilus. Accordingly, even if a different relative dies the only difference in the procedure is the order of the seven days of Aveilus and the seven days of Mishteh (that is, the Rabanan did not institute the leniency of observing the days of Mishteh first in such a case).
(b) The ROSH disagrees and says that if a different relative dies or if the food will not spoil, the wedding does not take place at all before the burial. Rather, the Chupah and Be'ilas Mitzvah are performed after the burial and the Aveilus. This also seems to be the view of RASHI (end of 3b).
How does the Rosh understand the Gemara that says that there is nothing wrong with doing Be'ilas Mitzvah before the burial (since the obligation of Aveilus has not yet taken effect)? The Rosh says that there certainly is something inappropriate with doing Be'ilah before burial; it is a disgrace to the Mes to delay the burial. Rather, the Gemara means that the Be'ilas Mitzvah is not an affront to the requirement to observe Aveilus (even if it is an affront to the honor of the Mes). Similarly, the RAMBAN (in Toras ha'Adam) and the RASHBA write that during the period of Aninus, before the burial, Be'ilah indeed is generally prohibited, and when the Gemara says that before the Aveilus takes effect doing Be'ilah is not an affront to the Aveilus, it means that it is an affront to the Aninus, but not to the Aveilus. Therefore, where there is no loss of money, it is not permitted to perform the Chupah and Be'ilas Mitzvah before burying the dead.
This argument seems to reflect a basic difference in opinion concerning how the Rabanan were lenient to allow the marriage in the case of the death of the father of the Chasan or the mother of the Kalah. The RIF seems to understand that the Rabanan overrode the laws of Aveilus by instituting that the seven days of Mishteh override the Aveilus. Therefore, neither the Chupah nor the Be'ilas Mitzvah had to take place before the burial, because the Rabanan could have simply instituted to override the Aveilus and perform the Chupah and Be'ilas Mitzvah after the burial. Since the Rabanan instituted that the Chupah be done before the burial, it must be that something is gained by doing so -- that is, by instituting that the Chupah and Be'ilas Mitzvah be done before the burial, the Rabanan avoided having to override the Halachos of Aveilus d'Rabanan, and the Chupah is being done entirely b'Heter (without overriding anything). (Apparently, there is no Isur Be'ilah during Aninus, either because Nisu'in and Be'ilah are not prohibited during Aninus, or because in this specific situation Be'ilah is not prohibited during Aninus, as the SHITAH MEKUBETZES on 4b explains.)
Rashi (4a, DH u'Poresh), however, has a completely different understanding. Rashi explains that the leniency was simply to allow the Chupah and Be'ilas Mitzvah to take place during Aninus. Once the Chupah is performed, it "causes the Chasunah to take effect" and it becomes like a festival, a Regel, for the Chasan. Because the Chupah creates a Regel for the Chasan, it is the Chasunah that overrides the Aveilus, and that is why the seven days of Mishteh precede the days of Aveilus. Therefore, in a case in which it is not necessary for the seven days of Mishteh to precede the Aveilus (i.e. where there is no financial loss involved), the Rabanan do not permit the Chupah and Be'ilas Mitzvah to be performed before the burial.
Another practical difference between Rashi and the Rif may exist a situation in which a relative -- not the father of the Chasan or the mother of the Kalah -- passes away after the Chupah and Be'ilah Rishonah. According to Rashi, the seven days of mourning should be postponed until after the seven days of festivity, since the celebration already started. According to the Rif, the seven days of mourning should be observed immediately. In this case, Rashi's opinion would be the lenient one, and the Rif's would be the stringent one.
HALACHAH: The SHULCHAN ARUCH (YD 342:1) rules like Rashi and the Rosh, that Chupah and the Be'ilas Mitzvah are not permitted before the Aveilus begins. The DERISHAH rules, similarly, that if the relative died after the Chupah and the days of festivity had already begun, the rest of the seven days of festivity are observed before the Aveilus.
(In a case in which the relative died immediately after the Chupah but before the seven days of festivity began, the Acharonim argue whether the Aveilus precedes the Mishteh or not -- see TAZ, NEKUDOS HA'KESEF, and others. The conclusion of the Acharonim seems to be that the seven days of Mishteh precede the Aveilus, as Rashi implies. See DIVREI SOFRIM YD 342:38.)