1) A ROCK WITH A "TZIYUN" OF A GRAVE
QUESTION: Rav Yehudah says that one who finds a stone marked with a Tziyun for Tum'ah may assume that only the area directly beneath the stone contains the grave.
How does Rav Yehudah understand the Beraisa earlier (5b) which states that a marker of Tum'ah is placed in front of the area which contains the grave and not directly above it? According to the Beraisa, one who finds a marked stone should assume that the grave is behind the stone and not directly beneath it.
ANSWERS:
(a) RASHI answers that a Tziyun normally is placed in front of the site of the grave, as the Beraisa says, because a person tends not to notice the Tziyun until he is standing directly over it. If an ordinary Tziyun would be placed directly on top of a grave, it would be ineffective in preventing people (and objects) from becoming Tamei; a person would not notice it until he is already standing over the grave. However, when the Tziyun is placed on a stone which is higher than the ground, a person notices the Tziyun before he walks over the stone. Therefore, a Tziyun on a stone may be placed directly over the source of Tum'ah. (In fact, it is even preferable to place it there, in order to minimize the area designated as Tamei, as the Gemara says earlier (5b).)
(b) The TOSFOS HA'ROSH quotes the Yerushalmi in Shekalim which explains that when the Beraisa says that a Tziyun should not be placed directly over the Tum'ah, it means that it should be placed not only on the area of the Tum'ah but even past the area of the Tum'ah. The periphery of the Tziyun is outside of the Tum'ah, but the Tum'ah indeed is under the marked area of the Tziyun itself.
Accordingly, both statements are true. The outer edge of the Tziyun is beyond the Tum'ah, while the inner part of the Tziyun is directly above the Tum'ah. This is also the opinion of the RAMBAM (Hilchos Tum'as Mes 8:9).

6b----------------------------------------6b

2) WATERING A "SEDEH GRID"
OPINIONS: In the Mishnah, Rebbi Eliezer ben Yakov and the Chachamim argue about the Halachah in two cases. In the first case, Rebbi Eliezer ben Yakov maintains that when one waters the trees in his field, he is prohibited from watering the rest of his field, while the Chachamim maintain that he is permitted to water the rest of the field. In the second case, Rebbi Eliezer ben Yakov prohibits watering seeds which received no water before Chol ha'Mo'ed, while the Chachamim permit it. The Beraisa mentions a third case in which the Tana Kama (presumably Rebbi Eliezer ben Yakov) and the Chachamim argue: the Tana Kama prohibits watering a "Sedeh Grid" and the Chachamim permit it.
What is a "Sedeh Grid" and what are the reasons to permit or prohibit watering it?
(a) TOSFOS, the NIMUKEI YOSEF, and other Rishonim explain that "Sedeh Grid" is another term for a Beis ha'Ba'al, a field which does not need artificial irrigation. The word "Grid" means "dry" and refers to a field which does not need constant watering. This also seems to be the intention of Rashi.
They explain (like Rashi) that Rebbi Eliezer ben Yakov and the Chachamim in the Mishnah argue whether Melachah on Chol ha'Mo'ed for the sake of Harvachah, making a profit, is permitted. The Chachamim -- who permit Melachah for the sake of Harvachah -- follow the view of Rebbi Meir (2a) who explicitly permits Melachah for the sake of Harvachah. Their argument in the case of a Sedeh Grid follows logically from their argument with regard to Harvachah. Since watering a Beis ha'Ba'al is for the sake of Harvachah, Rebbi Eliezer ben Yakov prohibits it and the Chachamim permit it.
(b) TOSFOS cites others who explain that the argument in the Beraisa with regard to a Sedeh Grid is not related to whether Harvachah is permitted. The Tana Kama in the Beraisa who argues with the Chachamim is not Rebbi Eliezer ben Yakov. The Tana Kama of the Beraisa is a third Tana who is more stringent than Rebbi Eliezer ben Yakov (who would permit watering a Sedeh Grid). (Accordingly, even though the Halachah follows the view of Rebbi Eliezer ben Yakov in the cases of the Mishnah, one nevertheless is permitted to water a Sedeh Grid.)
These Rishonim define "Sedeh Grid" as a type of field which has characteristics of a Beis ha'Shalchin and characteristics of a Beis ha'Ba'al. It is not exactly like a Beis ha'Ba'al because supplying it with more water will not cause it to bear more fruit. However, more water will cause it to produce fruit faster, and in that sense it is not exactly like a Beis ha'Shalchin (where more water merely saves the field from drying out but does not affect the growth of its fruit). The Tana Kama prohibits watering a Sedeh Grid because he considers the act to be for the sake of Harvachah. The Chachamim (who permit it) do not consider the act to be for the sake of Harvachah because fruit which ripens faster is not as tasty (as it does not ripen fully), and thus one does not benefit from watering such a field. Watering a Sedeh Grid is not considered Harvachah; rather, one merely "changes" the fruit from one type of fruit to another.
(c) The RITVA, NIMUKEI YOSEF, and TOSFOS HA'ROSH cite a Yerushalmi which says that the argument in the Mishnah between Rebbi Eliezer ben Yakov and the Chachamim is unrelated to Harvachah. Neither Rebbi Eliezer ben Yakov nor the Chachamim permit Melachah for the sake of Harvachah. Rather, their argument involves whether watering the entire field (or watering seeds that were not watered before Chol ha'Mo'ed) is considered a Davar ha'Aved.
These Rishonim define a Sedeh Grid as a Beis ha'Ba'al, like Tosfos. Both Rebbi Eliezer ben Yakov and the Chachamim agree with the Beraisa which says that one is not permitted to water a Sedeh Grid. What is the meaning of the words at the end of the Beraisa, "v'Chachamim Matirin ba'Zeh uva'Zeh" -- "the Chachamim permit both this and this"? The RITVA explains that these words are not part of the Beraisa but are a citation from the Mishnah which the Gemara is preparing to discuss.
Alternatively, the NIMUKEI YOSEF explains that these words refer back to the two cases mentioned in the Mishnah and not to the third case (Sedeh Grid) which is mentioned in the Beraisa. Hence, everyone agrees that watering a Sedeh Grid is prohibited. (See following Insight.)
The Tosfos ha'Rosh suggests that even if the Yerushalmi's understanding of the Mishnah is correct, it still is possible that Rebbi Eliezer ben Yakov and the Chachamim argue about a Sedeh Grid. They do not argue whether or not Harvachah is permitted (as in (a) above), but whether or not a Sedeh Grid is considered a Davar ha'Aved. The Rosh defines "Sedeh Grid" as a Beis ha'Ba'al which has not received water for an exceptionally long time (as Rashi on the Rif explains). The Chachamim maintain that such a field is considered a Davar ha'Aved and they permit watering it on Chol ha'Mo'ed even though it is a Beis ha'Ba'al. Rebbi Eliezer ben Yakov maintains that watering such a field on Chol ha'Mo'ed is prohibited. His reasoning is that since the field is not usually watered manually, watering it now will not help it recover.
3) WATERING A VEGETABLE GARDEN ON CHOL HA'MO'ED
OPINIONS: Ravina infers from the laws recorded in the Mishnah and Beraisa that one is permitted to "sprinkle a Tarbitza" (vegetable garden) with water. He reasons that if one is permitted to water a Sedeh Grid and thereby cause the fruit to ripen faster, then one also must be permitted to water his vegetables to make them ripen faster.
The Tana'im in the Beraisa argue with regard to whether one is permitted to water a Sedeh Grid (see previous Insight). On which opinion in the Beraisa does Ravina rely to prove his ruling? Moreover, does the fact that Ravina sides with one opinion prove that the Halachah follows that opinion?
(a) RASHI explains that Ravina proves his ruling from the Chachamim who permit one to water a Sedeh Grid (which is the same as a Beis ha'Ba'al). (The Chachamim follow the view of Rebbi Meir who permits one to water his field for the sake of Harvachah, profit).
Rashi implies that the Halachah follows the view of Rebbi Meir. Since Ravina rules like the Chachamim who agree with Rebbi Meir, one is permitted to water a Beis ha'Ba'al for Harvachah on Chol ha'Mo'ed.
(b) TOSFOS (DH Shari) suggests that although Ravina adduces proof for his ruling from the opinion of the Chachamim who permit one to water a Beis ha'Ba'al, this does not mean that Ravina rules like the Chachamim. Rather, Ravina does not permit one to water a vegetable garden but only to sprinkle it with water. He proves that one may sprinkle water on a vegetable garden from the view of the Chachamim who go so far as to permit one to water a Beis ha'Ba'al. If the Chachamim rule so leniently, then it is logical that no one -- even the Tana who argues with the Chachamim -- would be so stringent as to prohibit one from sprinkling water in a Beis ha'Ba'al.
Alternatively, Ravina understands that among the Chachamim who permit one to water a Sedeh Grid is Rebbi Eliezer ben Yakov. He permits it because watering such a field is not considered a genuine form of Harvachah (see (b) of previous Insight). The Tana Kama who prohibits one from watering a Sedeh Grid is not Rebbi Eliezer ben Yakov but another Tana. The Halachah therefore is in accordance with the view of the Chachamim (and Rebbi Eliezer ben Yakov) who permit one to water a Sedeh Grid, but it is not in accordance with the Chachamim who argue with Rebbi Eliezer ben Yakov in the Mishnah and permit one to water even a Beis ha'Ba'al.
(c) However, RABEINU CHANANEL, the RIF, and most Rishonim explain that Ravina's ruling is not based on the Halachah of Sedeh Grid at all. Rather, he bases his ruling on the other cases mentioned in the Mishnah. The RITVA and NIMUKEI YOSEF write that his ruling is based on the Halachah that one may water a Sedeh Metunenes. RABEINU CHANANEL says that it is based on the allowance to water seeds that received water before Chol ha'Mo'ed. In these cases, even Rebbi Eliezer ben Yakov permits one to water the plants on Chol ha'Mo'ed.
When, immediately after Ravina's statement, the Gemara compares Ravina's case of a vegetable garden to the Beraisa's case of Sedeh Grid, it is rejecting (and not supporting) Ravina's ruling. The Gemara is asking that watering a vegetable garden cannot be compared to the cases in which Rebbi Eliezer ben Yakov permits watering: in the case of the vegetable garden, one merely causes the vegetables to ripen earlier, which is a case of Harvachah and not Davar ha'Aved, like the case of a Sedeh Grid, and therefore it should be prohibited (see (c) of previous Insight). According to this interpretation, the Halachah will not follow Ravina, but will follow Rebbi Eliezer ben Yakov.

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