A Beraisa describes what happens if a mourner first comes in the middle of a Shiv'ah that his family has already started to observe:

If he came from nearby during the first three days he finishes Shiv'ah along with the others. If he came from afar, or if he came during the last four days, he begins seven days of Shiv'ah from the day he arrives.

R. Shimon disagrees, and says that if one comes from nearby, no matter when he comes (even on the seventh day) he finishes with the others.

R. Yochanan placed a limitation on the law in the Beraisa (1:a:1), that said that if a mourner came from nearby in the first three days he finishes along with the others: This only applies when the central figure of the family (e.g., the oldest son) is there with the original group. Otherwise the newcomer must begin seven days of Shiv'ah when he comes.

Question: What if the newcomer is himself the central figure, and the reason he is joining the others late is that he accompanied the bier to the burial site (which was some distance away), while the others went home after taking leave of the bier near their house? Does the newcomer finish with the others (because he was, after all, dealing with the deceased all the time), or does he count seven days of his own?

Answer: He finishes with the others.

Question: There is a Beraisa that says otherwise, that he counts seven days of his own.

Answer: It depends when he joins the others. If it was during the first three days he finishes with them; if it was after this he counts seven days of his own.

(Rava): When people do not go all the way to the burial site, their mourning period begins as soon as they turn around to go home. (But when one does go to the burial site, the mourning doesn't start until the coffin is covered.)

(Rebbi): When R. Shimon said that the newcomer finishes with the others even if he comes (from nearby) on the seventh day, this is only if he got to the house of mourning while there were still consolers there. If he missed the consolers, he counts seven days of his own.

Unresolved question: What if the consolers were still in the houses, but had already gotten themselves ready to leave?

Someone said two things in the name of R. Zeira (or R. Chiya bar Aba):

The Halachah is like R. Shimon in regard to mourning (in the Beraisa above, 5:a:2)

The Halachah is like R. Shimon ben Gamliel in regard to Treifos (R. Shimon ben Gamliel permitted an animal whose intestines were pierced and then stopped up with intestinal secretions).

Someone went to Israel, went to the quoted rabbi, and asked him if these statements were true. He replied: "Regarding Treifos I said the exact opposite, that the Halachah is against R. Shimon ben Gamliel. Regarding mourning, it is a disagreement of sages whether to follow R. Shimon or not."

Final ruling: The Halachah is not like R. Shimon ben Gamliel (regarding Treifos), but it is like R. Shimon (regarding mourning), because we always follow the lenient opinion in issues of mourning.

For other relatives it's alright to rush the burial, but not for a parent.

On Erev Shabbos or Erev Yom Tov it's alright to rush even for a parent.

For other relatives one need not cut down on his business (done by others for him - R. Chananel; or after Shiv'ah - Ritva), but for parents he must cut down.

For other relatives one need not bare his shoulder (by sticking his arm through the rip - R. Chananel), but for a parent he must.

One Gadol ha'Dor once refrained from baring his shoulder for his father because another Gadol ha'Dor was there and wanted to do so also (out of respect and empathy for the first Gadol ha'Dor), and the first Gadol ha'Dor did not want the other Gadol ha'Dor to go with a bared shoulder.

Some say that it was Rebbi Yakov bar Acha who's father died, and Rebbe who wanted to bare his shoulder along with Rav Yaakov bar Acha. Some say this story with the names reversed, but this is not likely because Rebbi's father was the Nasi, and if he died, indeed everyone (including Rebbi Yakov bar Acha) is supposed to bare his shoulder for the Nasi.

For other relatives it's alright to have a haircut after Shloshim, but for a parent he must wait until his friends tell him he looks unkempt.

For other relatives it's alright to go to a celebration after Shloshim, but for a parent it is forbidden for twelve months.

First version of Rabah bar bar Chanah: When we say that it's alright to go to a celebration after Shloshim for other relatives, we only mean a social gathering, but not a real party (like a wedding).

Question: A Beraisa says parties and social gatherings are forbidden only during Shloshim. The question remains unanswered.

Second version of Rabah bar bar Chanah: When we say that it's alright to go to a celebration after (but not before) Shloshim is over for other relatives, this means real parties, but a social gathering is permitted immediately after Shiv'ah.

Question: A Beraisa says that parties and social gatherings are forbidden during Shloshim.

Answer: It depends. People take turns hosting social gatherings. If it's the mourner's turn he may do it (during Shloshim), to fulfill his obligation to the others. But if it's not his turn he may not participate.

For other relatives the rip of the Keri'ah is a tefach (a hand's width), but for a parent the rip must be big enough until it bares the heart.

The Biblical source that a Keri'ah has to be a tefach is: "And David took hold of his garments and tore them." "Took hold" implies at least a tefach.

For other relatives only the outermost garment is ripped, but for a parent all garments being worn are ripped, even ten.

The Apikarsus (a headdress that slopes down over the shoulders and chest - Rashi/Rif) need not be ripped.

Men and women must both do Keri'ah

R. Shimon ben Elazar says that a woman rips the bottom garment, turns it around, and then rips the top garment (so as not to reveal herself).

For other relatives the Keri'ah may be done starting from the neck hole (Rashi) or from below it, but for a parent it must be done starting from the neck hole.

R. Yehudah says that all Keri'ahs must be done starting from the neck hole.

The Biblical source for R. Yehudah is: "He took hold of his garments and tore them into two" implying that the rip actually tore open the garment in two.

For other relatives it's alright to baste the rip after Shiv'ah and to sew it completely after Shloshim, but for a parent it is forbidden to baste until after Shloshim and it is forbidden to sew it completely forever. A woman may baste the rip immediately, for modesty.

(R. Yochanan): For other relatives it's alright to rip with an implement (knife, razor, etc.), but for a parent it must be done with the bare hand.

(R. Yochanan): For other relatives it's alright to do the rip "inside" (Rashi: on an inner garment; others: in private, where no one sees), but for a parent it must be done "outside" (on the outer garment, or in public).

(R. Chisda): For a Nasi one must do Keri'ah "outside" (see above, 3:k).

Question: A Beraisa says that the mourning held for great rabbis is like the mourning for parents only in respect to the prohibition to sew up the rip (see above, 2:i), implying that in other respects mourning a great rabbi is not equated to mourning a parent. (The rip should therefore be allowed to be done "inside".)

Answer: The Beraisa is talking about other great rabbis, not a Nasi.

Here there is a story with R. Chisda and R. Chanan and the death of a Nasi.

For a rabbi the right shoulder is bared; for an Av Beis Din the left shoulder is bared; for a Nasi both shoulders are bared.

Here there is a Beraisa about mourning for rabbis. It makes several points.

When a rabbi dies, his Beis Midrash (Yeshiva) stops its learning.

When an Av Beis Din dies, all Batei Midrashos in town stop their learning.

When a Nasi dies, all Batei Midrashos in all places stop their learning. Furthermore, minyanim are not held that Shabbos for prayers, only for reading the Torah. (The rest of the day people should sit around being sad, not take strolls.)

One should not give Torah lessons (Halachah or Agadah) in a mourner's house. But R. Chananyah ben Gamliel did do this.