PEOPLE WHO BECOME PERMITTED AT NIGHT
(Mishnah): An Onen immerses and eats Pesach at night; this is forbidden regarding other Kodshim.
One who heard that he lost a relative [a while ago] or gathers bones [of a parent for reinterment - both of these mourn that day, but not at night] immerses and eats Kodshim [at night].
Beis Shamai say, if someone converted on Erev Pesach, he immerses and eats Pesach at night;
Beis Hillel say, one who takes leave of his foreskin (circumcises) is like one who takes leave of a grave (he requires Taharah like a Tamei Mes).
(Gemara) Question: Why is Pesach permitted but not Kodshim?
Answer: The Tana holds that Aninus applies mid'Rabanan at night;
Chachamim did not apply this stringency to Pesach, for which there is Kares [for not bringing it]; they apply their stringency regarding [eating other] Kodshim, which is a regular Mitzvas Ase.
(Mishnah): One who heard that he lost a relative...
Question: One who gathers bones [becomes Tamei Mes, he] needs Haza'ah on days three and seven!
Answer: It means, one who had someone gather bones for him...
(Mishnah): If someone converted...
(Rabah bar bar Chanah): They argue about an Arel Nochri [who circumcised and converted] - Beis Hillel decree, lest he will become Tamei Mes next Erev Pesach, and think that he can immerse and eat Pesach at night, just like this year (even though [presumably] he was exposed to Tum'as Mes before conversion, and never was sprinkled on);
He will not realize that this year immersion sufficed because he was not Mekabel Tum'ah while he was a Nochri, but next year he is Mekabel Tum'ah [and needs Haza'ah].
Beis Shamai do not decree.
All agree that if a Yisrael circumcises, he immerses and eats Pesach at night - we do not decree on account of an Arel Nochri (the Yisrael must immerse because until now he was forbidden to eat Kodshim - Chagigah 24B; see Tosfos Chodoshim).
Support (Beraisa - R. Shimon ben Elazar): Beis Shamai and Beis Hillel agree that if a Yisrael circumcises, he immerses and eats Pesach at night - they argue about an Arel Nochri:
Beis Shamai say, he immerses and eats Pesach at night;
Beis Hillel say, one who takes leave of his foreskin is like one who takes leave of a grave.
WHICH DECREES ARE RELAXED ON ACCOUNT OF KARES?
(Rava): Regarding Arel, Haza'ah and a knife, Chachamim upheld their enactments even regarding Kares (preventing bringing Pesach); regarding Onen, Metzora and Beis ha'Pras, they did not uphold their enactments regarding Kares (as we explain):
Arel - like above (one who converted on Erev Pesach is like a Tamei Mes, he may not bring Pesach);
Haza'ah (sprinkling Mei Chatas) is Shevus (forbidden mid'Rabanan on Shabbos), it is not Docheh Shabbos even if it is necessary to enable one to Metaher in time to offer Pesach;
A knife - (Beraisa): Just like one may not bring [a knife to circumcise on Shabbos] via Reshus ha'Rabim, it is forbidden via roofs, Chatzeros and Karfifos (enclosed areas without a roof, even though the Isur to transfer through these Reshuyos is mid'Rabanan; one who has not yet circumcised his son may not bring Pesach.)
Onen - like above (he may not eat Kodshim at night, but he may eat Pesach);
Metzora - (Beraisa): If the eighth day of Taharas Metzora fell on Erev Pesach, and he had an emission of semen on that day, he immerses and eats [Pesach at night]:
Normally, a Tevul Yom may not enter the Ezras Nashim - in this case, he may (to stick his ear, thumb and big toe into the Azarah to complete his Taharah and enable him to bring Pesach);
[Machshirim for] an Ase with Kares (Pesach) override an Ase without Kares (that a Tevul Yom must leave the Ezras Nashim).
(R. Yochanan): Mid'Oraisa, there is not even an Ase (for a Tevul Yom to leave)!
Question: "Va'Ya'amod Yehoshafat...b'Veis Hash-m Lifnei he'Chatzer ha'Chadashah" - why is it called new?
Answer: They made a new decree, that a Tevul Yom may not enter Machaneh Leviyah (i.e. Ezras Nashim).
Beis ha'Peras - (Mishnah): Beis Shamai and Beis Hillel agree that one may check a Beis ha'Peras (a field in which a grave was plowed, we are concerned that bones were dragged around) for one who wants to [go through to] bring Pesach, but not to eat Terumah. (Mid'Rabanan, a Beis ha'Peras is like a cemetery - to enable one to bring Pesach, we are lenient.)
Question: How does one check it?
Answer (Rav Yehudah): A person may walk through a Beis ha'Pras by bending down and blowing the dirt before each step [to clear away any small bones that might be there].
(Rav Yehudah bar Ashi citing Rav Yehudah): If many people walked through a Beis ha'Pras, it is Tahor (we assume that any bones have been crushed to less than the Shi'ur to Metamei, i.e. the size of a barley seed).
IF PESACH WAS OFFERED FOR SOMEONE B'DERECH RECHOKAH
(Mishnah): If one was Tamei or far away and did not bring Pesach Rishon, he brings Pesach Sheni;
If he did not bring Pesach Rishon b'Shogeg or b'Ones, he brings Pesach Sheni.
Question: Since the law is the same, why does the Torah specify Tamei and Derech Rechokah?
Answer: These are exempt from Kares, and these (this will be explained) are Chayavim.
(Gemara - Rav Nachman): If one was far away and others slaughtered and did Zerikah for him [to come and eat at night], he fulfilled Pesach;
The Torah is merciful on (exempts) one who was far away, but if he brought Pesach, he will be blessed!
(Rav Sheshes): He was not Yotzei - he is precluded from Pesach, like a Tamei.
Support (Rav Nachman, for himself - Mishnah): If one was Tamei or far away and did not bring Pesach Rishon, he brings Pesach Sheni.
Inference: If he wanted, he could have brought Pesach Rishon (this refers to Derech Rechokah - since he is exempt, we must discuss a Tamei who could not bring Pesach)!
Rejection (Rav Sheshes - Seifa): If he was Shogeg or Ones and did not bring Pesach Rishon, he brings Pesach Sheni.
Question: Will you say that if he wanted, he could have brought Pesach Rishon - it says that he was Shogeg or Ones!
Answer: Rather, the Seifa discusses [without explicitly mentioning] Mezid with them (Shogeg and Ones);
Likewise, the Reisha discusses Onen with them (Tamei and Derech Rechokah; the Onen could have offered if he wanted)!
Support (of rejection - Rav Ashi - Seifa): These are exempt from Kares, and these are Chayavim.
Question: What case does this discuss?
It does not discuss Shogeg or Ones - they are not Chayav Kares!
Answer: Rather, it discusses Mezid and Onen.
Rejection: Rav Nachman can say that it only discuss Mezid;
Really, it should say Chayav (singular) - it says Chayavim for parallel structure with the Reisha, which says Peturim.