QUESTIONS: The Gemara says that at the moment Rebbi Akiva died, Rebbi was born. When Rebbi died, Rav Yehudah was born. When Rav Yehudah died, Rav Ashi was born. This succession teaches that a Tzadik does not leave this world until another Tzadik like him has been born, as the verse states, "The sun rises, and the sun sets" (Koheles 1:5) -- before the sun sets (i.e. before the Tzadik dies), another sun has risen.
(a) The verse describes the regular course of natural events, sunrise and sunset. What indication in the verse alludes to the birth and death of Tzadikim?
(b) Why does the verse compare the continuing succession of Tzadikim to the rising and setting of the sun, and not to any other event that expresses continuity?
(a) The IYUN YAKOV explains that if the verse intended solely to refer to the beginning and end of the day, it should have reversed the order -- "The sun sets, and the sun rises," because the day begins at nightfall with regard to all Halachic matters (except for Kodshim), and as the verse in the beginning of the Torah states, "It was night, and it was morning." From the change in the order of the verse, the Gemara sees an allusion to the death and birth of Tzadikim.
(b) The SEFER HA'MIKNAH explains that sunset does not indicate the end and demise of the sun, but rather it marks merely the moment the sun leaves man's range of vision. The darkness which descends at sunset is not a sign that the sun no longer exists, but that it has gone beyond man's present world. The same is true with the death of a Tzadik. The radiance of the Tzadik does not cease to exist when he dies. Rather, it continues in all of its grandeur and strength, but in Olam ha'Ba where man, from his perspective in this world, is unable to see it.
The Sefer ha'Miknah adds that there is a degree of Yeridas ha'Doros, a decrease in the spiritual quality of the generations, as the generations move farther away from the time the Torah was given at Har Sinai. The verse compares the rising of the new sun to the setting of the old sun to teach that the new Tzadik born into the new generation is comparable only to the "setting sun" of the previous generation. He does not shine with the same splendor with which the rising sun of the previous generation shined. (See Bava Basra 75a.)
OPINIONS: The Mishnah (69a) implies that only the Jews who ascended to Eretz Yisrael from Bavel are "b'Chezkas Kashrus," while Jews from other places are not "b'Chezkas Kashrus." Rav Yehudah in the name of Shmuel says that this is the view of Rebbi Meir, while the Chachamim disagree and say that Jews from all lands are "b'Chezkas Kashrus."
The Gemara relates an incident in which Ameimar ruled in accordance with the view of the Chachamim, as expressed by Rav Yehudah in the name of Shmuel, and permitted Rav Huna bar Nasan to marry a woman from an area outside of Bavel. The Gemara says that although a number of Amora'im dispute the ruling of Rav Yehudah in the name of Shmuel and maintain that the Chachamim do not argue with Rebbi Meir, Ameimar relied on Rav Zevid of Neharde'a who agreed with Shmuel's ruling.
What is the Halachah with regard to the "Chezkas Kashrus" of Jews who come from lands other than Bavel?
The SHULCHAN ARUCH (EH 4:2) rules like the Chachamim, that families from all lands are "b'Chezkas Kashrus" and one may marry a Jew from any family even l'Chatchilah. The BI'UR HA'GRA notes that although the Sugyos earlier in this chapter of Kidushin assume that "Kol ha'Artzos Isah l'Bavel" -- "all lands are considered 'Isah' when compared to Bavel," and the Gemara earlier on this Daf discusses the borders of Bavel with regard to Yuchsin (implying that all other lands are not like Bavel), the Halachah nevertheless follows the view of Rav Yehudah in the name of Shmuel since Ameimar ruled like that in practice.
When the Gemara states that all families are "b'Chezkas Kashrus," does it refer only to families that live among other Jews who, until today, are assumed to be part of the community of valid Jews and thus have a Chazakah of Kashrus, or does it refer even to families that come from remote places and that no one knew about until today?
The BEIS SHMUEL (EH 4:3) cites a Machlokes Rishonim on this matter. The TUR maintains that only a family previously known by the Jewish community is considered to have a "Chezkas Kashrus." If the family was not known, there is a fear of Mamzerus and Avdus.
The ROSH and RAMBAN maintain that even a family that was not known heretofore is considered to have a "Chezkas Kashrus" (except with regard to Pesulei Kehunah).
QUESTION: The Gemara cites a Beraisa which records a dispute between Rebbi Yosi and Rebbi Meir with regard to the status of Mamzerim and Nesinim in future times, when Mashi'ach comes. Rebbi Yosi says that Mamzerim and Nesinim will become Tahor, and Rebbi Meir says that they will not become Tahor.
Why does Rebbi Yosi maintain that Mamzerim will be permitted to marry into the Jewish people? The Torah explicitly states that "a Mamzer shall not come into the congregation of Hash-m" (Devarim 23:3). Rebbi Yosi certainly does not maintain that an Isur d'Oraisa will be uprooted in the future.
(a) The RASHBA explains that the purification of Mamzerim at the time of the arrival of Mashi'ach will be in the context of a "Hora'as Sha'ah," a temporary ruling necessary for the circumstances of the time. All Mamzerim alive at that time -- and only at that time -- will be allowed to marry into the Jewish people. After that time, however, the prohibition will take effect again (in the event that a child is born from a forbidden union). Although the Chachamim and prophets are not empowered to alter any Mitzvah, the concept of "Hora'as Sha'ah" enables them to suspend a Mitzvah temporarily (as in the case of Eliyahu ha'Navi at Mount Carmel, as described in Melachim I 18).
(b) The RITVA explains that the Gemara does not mean that a definite (Vadai) Mamzer will be permitted. Rather, the Gemara refers to "Mishpachos she'Nitme'u," families into which a Mamzer married, whose descendants' status is unknown. The Ritva points out that it is only Rebbi Yosi who rules that "once they have become mixed in, they have become mixed in." Rebbi Meir apparently disagrees with that allowance.
According to the Ritva, why does the Gemara question Rebbi Yosi's opinion from the verse, "v'Yashav Mamzer b'Ashdod" -- "And a Mamzer will dwell (Rashi: be separated) in Ashdod" (Zecharyah 9:6)? Perhaps the verse refers to a Vadai Mamzer! The Ritva explains that if the Mamzer in the verse would be a Vadai Mamzer, there would be no need to separate him since his Pesul would be known to all. The fact that a special act of separation needed to be made indicates that his status is that of a Safek Mamzer.