1) THE DIFFERENCE BETWEEN "CHOTETIN OSAN" AND "CHOTETIN L'SOCHAN"
QUESTION: The Gemara discusses doing Chatitah in a private water pit (Bor Shel Yachid) and in a public water pit (Bor Shel Rabim) on Chol ha'Mo'ed. Chatitah involves removing rocks and other debris from inside the pit. The Gemara quotes and explains several Beraisos which discuss this issue. It concludes that if one "needs the water," he is permitted to do Chatitah in a Bor Shel Yachid (see Chart, footnote 2). The last Beraisa quoted by the Gemara concludes that "one may do Chatitah to them (Chotetin Osan)... but one may not do Chatitah into them (v'Lo Chotetin l'Sochan)."
What is the difference between "Chotetin Osan," which is permitted, and "Chotetin l'Sochan," which is not permitted?
ANSWERS:
(a) The LECHEM MISHNEH (Hilchos Yom Tov 8:4) says that "Chotetin l'Sochan" must refer to an act that resembles digging (perhaps he means an act which increases the depth of the pit). In contrast, "Chotetin Osan" refers to an act of cleaning out the part of the pit which is already dug out.
(b) The MIRKEVES HA'MISHNEH explains that when the Beraisa says "Chotetin l'Sochan," the phrase "l'Sochan" ("into them") refers back to the "cracks" in the walls of the pit mentioned in the previous statement of the Beraisa ("v'Lo Shafin Es Sidkehen" -- "one may not smooth the cracks"). The Beraisa means that one may not clean out the cracks in the walls of the pit in order to plaster the walls. (However, see Chart, footnote 1.)
(c) The DIKDUKEI SOFRIM omits the words, "v'Ein Chotetin l'Sochan," from the text of the Gemara. Indeed, none of the Rishonim cite these words or explain the difference between the two types of Chatitah. It is logical to assume that these words did not appear in their text of the Gemara.

5b----------------------------------------5b

2) A FIELD IN WHICH A GRAVE WAS LOST OR PLOWED OVER
OPINIONS: The Gemara cites a Beraisa which lists the different circumstances in which a grave-marker is placed above an area where a corpse (or part of a corpse) is located. Based on the Beraisa, the Gemara concludes that since a "Beis ha'Pras" in which a grave was plowed over ("Sadeh she'Necherash Bah Kever") does not render a person Tamei through Tum'as Ohel (but only through Tum'as Heset), it needs no marker. A different type of Beis ha'Pras, a field in which a grave was lost ("Sadeh she'Ne'evad Bah Kever") but not plowed over is Metamei b'Ohel and thus it does need a marker.
The Gemara quotes another Beraisa which implies that a "Sadeh she'Necherash Bah Kever" does need a marker. The Beraisa states that if one finds a field marked as Tamei but does not know what type of Beis ha'Pras it is (he does not know whether it is Metamei b'Ohel or only Metamei b'Heset), he determines the status of the field based on the presence of trees. If the field contains trees, it is a "Sadeh she'Necherash Bah Kever" and is not Metamei b'Ohel. If it contains no trees, it is a "Sadeh she'Ne'evad Bah Kever" and is Metamei b'Ohel.
The Gemara asks that if a "Sadeh she'Necherash Bah Kever" does not need a marker, then why does one who finds a field marked as Tamei have any doubt about what type of field it is? It obviously is a "Sadeh she'Ne'evad Bah Kever."
The Gemara answers that it is true that a "Sadeh she'Necherash Bah Kever" needs no marker (because it is not Metamei b'Ohel). The Beraisa, however, refers to a field in which a Kever was once lost. If the field now contains trees, one may assume that the field was plowed over and is no longer a "Sadeh she'Ne'evad Bah Kever" but rather a "Sadeh she'Necherash Bah Kever," and it is not Metamei b'Ohel.
How does the presence of trees in a field indicate that the field was plowed over and that there is no corpse there?
(a) TOSFOS (DH Yesh Bah) explains the Beraisa based on a Tosefta (which is also a Mishnah in Ohalos 18:2-3). The Tosefta states that one may not plant trees in a "Sadeh she'Ne'evad Bah Kever," but he may plant vegetables and grains. In contrast, one may plant trees in a "Sadeh she'Necherash Bah Kever," but he may not plant vegetables and grains. (The reason why trees may not be planted in a "Sadeh she'Ne'evad Bah Kever" is either because trees bear fruit which catch the attention of bypassers, and we do not want people loitering in a field which has a grave (RASH to Ohalos 18:3), or because trees would spread the Tum'as Ohel with their branches (VILNA GA'ON ibid.).)
Accordingly, the presence of trees in the field is a reliable sign ("Siman") that no grave was lost in the field.
The SEFAS EMES and others question the explanation of Tosfos. The Gemara concludes that the Beraisa refers to a field in which a grave certainly was lost at one point in the past, but nevertheless the presence of trees indicates that it is only a field in which a grave was plowed over and it is not Metamei b'Ohel. If a grave was once lost in the field, how can the presence of trees indicate that it is not a "Sadeh she'Ne'evad Bah Kever"? It is known for certain that there is a grave in the field and, nonetheless, trees were planted there unlawfully.
The RASH (end of Ohalos 18:5) explains that if the field contains trees, we may assume that the grave must have been found and the bones removed before the trees were planted, since people know that trees may not be planted in a field which contains a lost grave. However, according to the Rash, why is the field considered a "Sadeh she'Necherash Bah Kever"? It should not be Metamei at all since the marking was made only because of the grave that was once lost there, but the grave has since been removed from the field! The Rash explains that if the people had removed all traces of the corpse, they indeed would have removed the mark indicating that the field is Tamei. Since they left the mark, it must be that the grave was plowed over before it was removed and they were not able to ensure that all remnants of the corpse were removed. Nevertheless, trees may be planted in such a field. Consequently, when there are trees in the field, the marking of the field indicates the Tum'ah of a plowed-over grave.
Alternatively, the Rash suggests that the presence of trees in the field shows that the people who first marked the field as Tamei simply made a mistake. There really was no lost grave there; the people who refrained from planting there in the past did so under a mistaken assumption.
(b) RASHI here (and in Kesav Yad) explains that the presence of trees in the field is not a sign that no grave was lost in the field. Rather, it is cause to be Metaher the field from Tum'as Ohel.
In what way do trees actually cause the field to be Tahor from Tum'as Ohel?
Trees cannot be planted in a field unless the field is first plowed. Hence, the presence of trees in the field indicates that the field was plowed over, and any grave that was there must have been destroyed by the plow. In that way the trees make the field into a "Sadeh she'Necherash Bah Kever."
REBBI AKIVA EIGER (in Chidushim), the NACHALAS DAVID, and the SEFAS EMES question this explanation. Even if a field was plowed, it is likely that traces of the corpse still remain. While it is possible that no flesh remains on the corpse and that there is no significant portion of the corpse left in one place, it is more likely that at least a k'Zayis of flesh remains, or a spine, skull, or a "Rova Kav" of bones remains, which is Metamei b'Ohel. Why does Rashi say that there certainly is no Tum'as Ohel present when the field was plowed over?
The answer to this question may be inferred from the words of TOSFOS in Kesuvos (28b, DH Beis ha'Pras), who gives the same explanation as Rashi. Tosfos explains that even a "Sadeh she'Ne'evad Bah Kever" is Metamei b'Ohel only mid'Rabanan: the field is considered a Reshus ha'Rabim, and the rule is that "a Safek Tum'ah in Reshus ha'Rabim is Tahor" mid'Oraisa. Why did the Rabanan decree that the field is Tamei in this case, if mid'Oraisa it is Tahor? Tosfos answers that since the field will always be in existence and the Safek Tum'ah will always exist, the Rabanan decreed the field Tamei. Only a temporary question of a Safek Tum'ah in Reshus ha'Rabim is deemed Tahor (even mid'Rabanan). A permanent situation of a Safek Tum'ah in Reshus ha'Rabim, however, is deemed Tamei by the Rabanan. (The RASH in Ohalos 18:3 proposes a similar distinction.)
If the Tum'ah of the field in which the grave was lost is mid'Rabanan, perhaps the Rabanan ruled that a person who walks into such a field after it was plowed is Tahor because of a Sfek Sfeika: the first doubt is that perhaps the lost grave is not in the area in which the person walked; the second doubt is that even if the grave was in the area in which the person walked, the plow might have crushed so much of the bones (and the flesh might have decomposed) such that it no longer is Metamei b'Ohel.
However, according to this understanding, a novel Chidush emerges according to Rashi's explanation. If a field contains trees (which indicate that the field is one which had a grave which was plowed over) and one walks the entire length and width of the field, covering all parts of the field, he cannot rely on the Sfek Sfeika. Since he walked over every part of the field, he definitely walked over the grave. There is only one doubt left -- was the grave sufficiently intact to be Metamei b'Ohel or not? In such a case (of only one Safek), he indeed should be Tamei. Similarly, if one walked into a field covered by an awning which extended over the entire field, only one doubt remains. The awning acts as an Ohel over the entire field and spreads Tum'ah, and the only doubt left is whether the corpse is intact enough to be Metamei b'Ohel. Perhaps Rebbi Akiva Eiger and the other Acharonim do not accept this approach because no such Tum'ah is mentioned in the Gemara, Beraisa, or by Rashi.
Another difficulty with this approach is that although it explains the conclusion of the Gemara (that the plowed field once contained a lost grave), it does not explain the Gemara's original assertion that a plowed field is Tahor even when the grave in the field was known and was not lost. If the site of the grave is known, why should it not be Metamei after it is plowed over?
This difficulty may be resolved as follows. The Beraisa discusses the case of a person who came to a marked field and was unsure what type of Beis ha'Pras it was. Why was he unsure? He simply could have looked for the location of a grave inside the field. If he saw a grave, he would have assumed that the rest of the field was Tamei (as a "Sadeh she'Necherash Bah Kever" which is Metamei only through Tum'as Heset) because the corpse underneath the grave was plowed. If he saw no grave, he would have known that the rest of the field was Tamei with Tum'as Ohel (as a "Sadeh she'Ne'evad Bah Kever") because the grave was lost in the field. (There is no reason to assume that there once was a grave in the field (and thus the field is marked) but it was disinterred.)
The answer to this question is that even when there is no noticeable grave in the field, the field may contain a grave which was plowed. The grave was lost and then the field was plowed, and thus it is not Metamei with Tum'as Ohel.
Accordingly, even before the Gemara's conclusion it was known that the field originally contained a lost grave which was plowed over and that a Sfek Sfeika situation was thus created (as described above). The Gemara's conclusion merely introduces the possibility that the field was already marked as a Beis ha'Pras (due to the lost grave) before the grave was plowed over. This is in contrast to the Gemara's initial assumption that the field was marked only after the grave was plowed over. (M. KORNFELD)

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