1) "THOSE WHO WALK ON TWO LEGS"
QUESTION: The Gemara discusses the status of the blood and milk of a human being -- "Mehalchei Shtayim" ("those who walk on two [legs]") -- with regard to whether one may eat or drink them. Why does the Beraisa refer to a person as "Mehalchei Shtayim" in this instance, instead of simply calling him a "person" ("Adam")? (TOSFOS YOM TOV, Bikurim 2:7)
ANSWERS:
(a) The TOSFOS YOM TOV (Bikurim 2:7) answers that the term "Adam" sometimes refers only to a Jew. Hence, had the Gemara used the term "Adam" one might have thought that these laws apply only to the blood and milk of a Jew. The Gemara uses the term "Mehalchei Shtayim" to make it clear that this law refers to all people.
(The RISHON L'TZION asks that Tosfos in many places mentions that when the term "ha'Adam" (with the prefix "Ha") is used it includes all humans, both Jews and others; if so, the Beraisa could have used the term "ha'Adam.")
(b) The TIFERES YISRAEL quotes RAV YAKOV EMDEN who explains that the term "Mehalchei Shtayim" is used in order to include in this category the "Adnei ha'Sadeh" (a creature referred to in Kil'ayim 9) which also walks on two legs like man and which, according to some, is Metamei b'Ohel like man (see Insights to Bechoros 8:1).
(c) The BEIS DAVID explains that since the Gemara discusses animals in the same context here as it discusses man, it considers it to be degrading to use the term "Adam" (as if to say that "Adam" is just another species of animal). In order to avoid referring to "Adam" when relating solely to the animalistic, non-reasoning qualities of man, it uses the term "Mehalchei Shtayim."
2) AN ACT PROHIBITED BECAUSE OF "MAR'IS HA'AYIN" EVEN IN PRIVATE
QUESTION: The Gemara rules that if a gutter pipe on the roof of one's house becomes clogged, thus causing water to flood the roof and drip into the house, a person is permitted to kick away the debris on Shabbos covertly ("b'Tzin'a," in private) in order to unclog the pipe. It is not appropriate to do so publicly, apparently because those who see him do it might not realize that he is trying to clear out the pipe to prevent a loss, and they will think that he is desecrating Shabbos by fixing his pipe.
Rav in Beitzah (9a) teaches a general principle that "anything which is prohibited by the Rabanan is prohibited even in the innermost chambers." The Gemara's ruling here seems to contradict that rule, because it permits one to do an Isur d'Rabanan in private. How is the Gemara here to be reconciled with that rule?
ANSWERS:
(a) Some Rishonim rule, based on this and similar statements in the Gemara, that the Halachah does not follow Rav and one is permitted to do something that others will think is prohibited (but which is really permitted) in private but not in public. (RAV NISIM GAON, cited by Tosfos to Avodah Zarah 12a, DH Kol Makom and by the Rosh, Shabbos 22:9, RABEINU EFRAIM, cited by the Ba'al ha'Itur, Hilchos Yom Tov section 4, the BA'AL HA'ME'OR in Beitzah 4b and Shabbos 28b of the pages of the Rif; the RE'AH in Beitzah 9a)
The Rishonim prove that Rav's opinion is not accepted l'Halachah from the Yerushalmi (Kil'ayim 9:1).
(b) Most Rishonim, however, rule in accordance with Rav's prohibition (including the RIF, Shabbos 146b, and RAMBAM, Hilchos Shabbos 22:20, Hilchos Yom Tov 5:4). They differentiate between the case of the Gemara here and the cases to which his rule applies. As an example for where Rav's rule applies, the Gemara in Beitzah (9a) cites a Beraisa in which the Tana Kama permits one to spread out clothes to dry in the sun on Shabbos when it is done in a private place. Spreading out clothes to dry in a public area, however, is prohibited because of "Mar'is ha'Ayin" -- people will suspect that the person is not only drying his clothes on Shabbos but that he washed his clothes on Shabbos as well. Rebbi Elazar and Rebbi Shimon prohibit spreading out one's clothes even in private because they maintain that whenever there is a concern for Mar'is ha'Ayin, the act is prohibited even in the innermost chambers of one's home.
1. TOSFOS here explains that even if one fixes his pipe in a manner that is not prohibited, he transgresses only an Isur d'Rabanan because he fixes it in an unusual manner (with his foot). Therefore, the Rabanan did not prohibit it when done in private. In the case in Beitzah, on the other hand, people will suspect that he did something that is Asur d'Oraisa, and therefore the Rabanan prohibited it even in the innermost chambers.
2. Others note that there is a basic difference between the problem of Mar'is ha'Ayin in the case in Beitzah and the Mar'is ha'Ayin in the case of the Gemara here. In Beitzah, the person did not actually wash his clothes on Shabbos. The concern is that people might mistakenly conclude that he washed his clothes on Shabbos, since they see him setting his clothes out to dry. In the case of the Gemara here, the person actually fixed his pipe on Shabbos, an act that might have been prohibited had he not done it to save himself from a significant loss, but people might not realize that he did it to prevent damage to his house. The prohibition against doing an act even in one's private chambers because of Mar'is ha'Ayin applies only to the former type of Mar'is ha'Ayin -- where people will think that he is doing something other than what he is actually doing. The reason for this difference is explained in various ways by the Rishonim.
The RASHBA in Beitzah (9a) explains that if a person is doing a permissible act, but people who see think that it is a prohibited act, the prohibition is not as severe, and he may do the act in his innermost chambers. Cleaning out a pipe to prevent damage in one's house looks like a prohibited act but is actually permitted. In contrast, if people who see him will suspect him of doing an act that is not permitted under any circumstances, the Rabanan are more stringent and prohibit the act even in one's innermost chambers.
The RAN in Beitzah (9a) differentiates between these two types of Mar'is ha'Ayin based on a different line of reasoning. He says that when an act is permitted by the Torah and the Rabanan prohibited it because others will think that the person is doing something wrong, it becomes prohibited even in one's innermost chambers. In the case of the Gemara here, however, the opposite logic applies. The act of cleaning a pipe is an act that is normally prohibited (mid'Rabanan). Here, the Rabanan were lenient and permitted one to clean the pipe in order to save his house and his enjoyment of Shabbos. In such a case, although the Rabanan found it necessary to permit the act, because of "Mar'is ha'Ayin" they limited the permit to doing it in private. (That is, because the Rabanan saw the need to permit the act, they did not prohibit it in private places.)
HALACHAH: Rav's principle is cited by the SHULCHAN ARUCH (OC 301:45), based on the rulings of the Rif, Rambam, and others (opinion (b) above).

60b----------------------------------------60b

3) WHEN MAY A NURSING MOTHER REMARRY
QUESTION: The Gemara says that Rav Nachman permitted women of the family of the Reish Galusa (the Exilarch) who were widowed or divorced to remarry while they had a nursing baby, on condition that they hired a nursemaid ("Menekes") to nurse the child. For those women, Rav Nachman suspended the decree which the Rabanan instituted to prohibit a nursing woman from remarrying before twenty-four months pass from the time of the birth of the child. His reasoning was that there was no fear that the baby would be left without a nursemaid, for no nursemaid would quit her job if she was working for the powerful family of the Reish Galusa.
The Gemara proves from a Beraisa that normally a woman is prohibited from remarrying within twenty-four months even if she gives her baby to a nursemaid. The Beraisa discusses "Havchanah" -- the requirement for a divorced or widowed woman to wait three months before she remarries. The reason why she may not remarry within three months is that she might be pregnant from her former husband, and if she marries before three months have passed the identity of the father of the child will be in doubt. However, the Beraisa says that even if the woman clearly could not have children from the first husband (such as a woman whose husband was out of town or in prison, was old, or she was barren), she still must wait three months before she remarries. From that Beraisa it is evident that when the Rabanan enact a prohibition for a reason, the prohibition remains in force even in cases where the reason does not apply ("Lo Plug Rabanan").
If the prohibition applies even where the reason does not apply, why does Rav Nachman permit the women of the family of the Reish Galusa to remarry within twenty-four months? Moreover, the Gemara says that a nursing mother may not remarry within twenty-four months even if the child dies within that time, because of the concern that a cruel mother might kill her child in order to remarry right away. Why does the Gemara need a reason to prohibit her from remarrying if her child dies? It should be prohibited because of the "Lo Plug" element -- the prohibition applies even when the reason does not apply, just as the prohibition applies even where the woman gives her child to a nursemaid!
ANSWERS:
(a) TOSFOS explains that if a woman stops nursing because her baby died or because she gave the baby to a nursemaid, the enactment that a nursing mother may not marry within twenty-four months no longer applies to her. The only reason why the Rabanan prohibited such women from remarrying immediately in a case where the baby died was a Gezeirah that a mother might kill her baby; in the case, where she gave the baby to a nursemaid, the prohibition of remarrying is due to a Gezeirah that the nursemaid might give the baby back to the mother. When a member of the family of the Reish Galusa gives a baby to a nursemaid there is no such concern, and that is why the women of the family of the Reish Galusa were permitted to remarry after giving the child to a nursemaid.
The MAHARSHA points out that the answer of Tosfos is very difficult to understand. If the concept of "Lo Plug" does not apply to a woman who gives her baby to a nursemaid, why does the Gemara prove from the fact that the Rabanan prohibited a barren woman from remarrying within three months after she was divorced or widowed that a nursing mother is prohibited to remarry within twenty-four months even when she gives the child to a nursemaid? Tosfos writes that "Lo Plug" does not apply when a child is given to a nursemaid! Moreover, why indeed does "Lo Plug" not apply when the child is given to a nursemaid?
The RITVA and TOSFOS HA'ROSH explain the answer of Tosfos more clearly. They say that "Lo Plug" does not apply when there is a clearly recognizable difference between a specific case and a general case that is normally prohibited. For example, when a child dies it is clear to all that the child is not alive and is not nursing, and thus "Lo Plug" does not apply and the mother may remarry right away. Similarly, if a woman from the family of the Reish Galusa gives over her child to a nursemaid, everyone knows that the nursemaid is afraid to break the agreement and the baby is assuredly in good hands. In contrast, when a woman from a normal family gives her baby to a nursemaid to be nursed, she still may not remarry right away because the nursemaid might give the baby back to her.
When a woman who is not from the Reish Galusa's family gives her baby to a nursemaid, and the nursemaid makes an oath that she will not break the agreement, may the woman remarry? Since the nursemaid makes an oath there is no longer any concern that she will break the agreement, and therefore the mother should be able to remarry! However, the Gemara says that in such a case, "Lo Plug" does apply, and it proves this from the fact that it applies to the requirement of Havchanah. The reason "Lo Plug" applies here is that it is not known to all that the nursemaid made an oath not to break her agreement, and therefore the mother may not remarry for twenty-four months.
(b) RASHI (DH b'Gezeirosav) does not seem to accept this reasoning. Rashi writes that the concept of "Lo Plug" teaches that a woman who gave birth may not remarry for twenty-four months whether she is nursing the child or not. It seems from Rashi's words that the "Lo Plug" here does not instruct us not to differentiate between a nursemaid who took an oath and a nursemaid who did not take an oath. Rather, Rashi understands the Gemara in its simple sense, that "Lo Plug" instructs us not to differentiate between a mother who is nursing and a mother who is not nursing (for any reason). Why, then, should the women of the Reish Galusa's family be permitted to remarry right away, and why should a woman whose child died be permitted to remarry (if not for the concern that she might kill her child)?
The answer might be that according to Rashi, "Lo Plug" does not create a blanket, all-encompassing prohibition. Rather, "Lo Plug" creates a prohibition (where the reason for the prohibition does not apply) only in cases where the cause for the original enactment is still applicable to at least a minimal degree. In order to prohibit a mother from remarrying because of "Lo Plug," there must be some possibility that she will need to continue nursing her child (or a similar concern, such as a concern that she might kill the child). Since the women of the Reish Galusa's family have absolutely no cause for concern, "Lo Plug" does not apply.
This explanation may be derived from the words of Rashi (DH Harei she'Haisah). Rashi writes, about all the women who are prohibited to remarry because of Havchanah, that "it is not common for them to become pregnant," which implies that it is remotely possible (i.e. that a Ketanah, an elderly woman, or a woman whose husband is in prison could become pregnant from her husband). That is why the Rabanan prohibited her from remarrying right away due to "Lo Plug." (In the case of an Akarah, a barren woman, the Rabanan might have prohibited a woman from remarrying within three months because of the concern that a healthy woman might make herself an Akarah in order to remarry.)
Accordingly, if a nursing mother gives her child to a nursemaid and the nursemaid makes an oath that she will faithfully nurse the child, perhaps the mother is permitted to remarry within twenty-four months. The RITVA indeed cites such an opinion. (M. Kornfeld)