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Rav Natan (15b) The Scope of Damage Prevention

  • Rav Reuven Taragin

Based on shiurim by Rav Reuven Taragin


I)  The Prohibition


            Although 'chatzi nezek' can no longer be officially collected (see last shiur), the gemara (15b) dictates the excommunication of a mazik's owner until he 'removes' the danger (by killing the animal, according to Rashi).  As basis for the ban, the gemara quotes Rav Natan's prohibition against raising menacing dogs or setting up rickety ladders.  Violation of the prohibition warrants the ban.


II)  Assumption

            The Shitta Mekubetzet (s.v. Mi-derebbe) and the Yere'im (siman 310) point out that Rav Natan's usage of the verse 'Ve-asita Ma'akeh le-gagekha; lo tasim damim be-vetekha' (Devarim 22:8 - 'And you shall make a railing for your roof; you shall not put blood in your house'), as basis for his prohibition, significantly expands the verse's scope.  The verse itself mandates only the installation of a guardrail surrounding a dangerous porch and includes no reference to dangerous objects.  Rav Natan obviously understood the porch case not as a limited exception, but as an archetype of all potentially dangerous situations.


III)  Basis


            Basis for his expansion can be found in the Sifrei (ibid. 19) which derives from the verse the responsibility to cordon off even one's pit.[1]  It seems that this issue was debated by the gemara (51a) which suggests two possible explanations for the limitation of the verse to homes of at least ten tefachim (handbreadths) height.  Initially, the gemara views the height requirement as reflective of the verse's relevance to only life-threatening situations.[2]  In response, the gemara explains the requirement as reflective of the verse's pertinence to only bona fide homes, that are at least ten tefachim high (as is the case regarding mezuza).  Rashi (s.v. Lav) justifies this suggestion by pointing out that the verse refers explicitly to homes.[3]

            A careful reading of Rav Natan's formulation reveals what he saw as the basis for his expansion.  Rav Natan quotes as his source not the aseh (positive commandment) with which the verse opens, but the Lav (negative prohibition) that concludes the verse.  This can be attributed to the broader formulation of the Lav which refers to any situation of potential 'damim' (bloodshed).


IV)  Two Tracks


            The significance of Rav Natan's linkage to the Lav hinges on the relationship between the Lav and aseh.  According to the Ramban (Kiddushin 34a s.v. Ve-ha), who assumes that the Lav merely reaffirms the aseh, once included through the Lav Rav Natan's cases fall under the rubric of the aseh as well.  However, according to Tosafot (ibid. s.v. Ma'akeh) and most Rishonim, who suggest distinctions between the aseh and the Lav, Rav Natan's cases may be prohibited by the Lav alone.  The Semak (siman 152)[4] suggests such a distinction by limiting the aseh to the particular situation it specifies - containing a porch.  The Lav, though, beyond confirming the aseh, mandates treatment of all dangerous situations - including those of Rav Natan. 


            The Netziv[5] uses this distinction to explain the Sifrei which requires safeguarding a pit, yet excludes buildings not normally used for lodging.  The Yere'im (siman 334) establishes the criteria for chiyuv to be the likelihood of danger, which depends on the frequency of use.  A pit must be protected, for it is frequented more than a house not designated for lodging.  The Devar Avraham[6], on the other hand, assumes the criteria to be a bona fide home and limits the pit case to one located in the vicinity of the home and, thus, considered part of it.  The Netziv, adopting the Semak's distinction between the aseh and the Lav, suggests that while the exclusion of the pseudo-home was regarding only the aseh, the inclusion of the pit was only regarding the Lav.  Although the aseh relates only to bona fide homes, the Lav relates to all dangerous situations.


            The Chayei Adam[7] uses this distinction to limit the scope of the berakha recited when constructing the rail.  Since birkhot mitzva are made only when fulfilling mitzvot aseh, he limits the berakha to the protection of porches, as opposed to other dangerous objects or situations.[8]

            This view of Rav Natan's reference to the Lav as exclusive can account for Tosafot's suggested distinction between the Lav and aseh.  Tosafot claim that, although the aseh applies irrespective of the circumstances of the porch's construction, the Lav pertains only to situations where the owner personally creates the danger with intent to neglect safety measures.[9]  Assuming the limitation of Rav Natan's statement to only the Lav, basis for Tosafot's understanding of the Lav's uniqueness can be brought from Rav Natan's emphasis on 'raising' ('yegadel') of menacing dogs and 'setting up' ('ya'amid') of rickety ladders.

            Acceptance of the distinctions of both Tosafot and the Semak (who quotes both together) we get a clear understanding of the relationship between the aseh and the Lav.  The aseh applies only to porches, under all circumstances; the Lav applies to all dangerous situations, but only when created with improper intent. 



Sources and Questions for shiur #20 Bava Kama on Tzerorot




1. Gemara BK (17a) Mishna … (19a) Teiku.

Rambam in his commentary to the mishna.

Rabbenu Chananel (19a) "Ba'i R. Abba bar Mammal … be-teiku."


2. Tosafot (17b) s.v. Nover.

Rashba (17b) s.v. Ve-tinfu.

Rashi (18b) s.v. De-dachik.


3. Rashi (17b) s.v. She-bazav; Yerushalmi 2:1 "R. Lazarkofer."

Tosafot s.v. Kol; Shitta Mekubetzet in the name of Rabbenu Yehonatan s.v. Ve-Rava.


4. Yerushalmi 2:2 "Tarnegol ha-porei'ach … nezek shalem."




1.  What aspect of tzerorot damages is 'diminished' and responsible for the reduction to half-nezek?

2.  How do most Rishonim understand R. Abba bar Mammal's question on (19a)?  How does the Rabbenu Chananel's explanation differ?

3.  Can there be tzerorot in avot other than regel?

4.  Which explanation of the 'zav' comparison seems more logical - Rashi's or Tosafot's?

5.  Does the Yerushalmi agree or disagree with the Bavli's view of an animal which breaks a utensil with its 'braying?'

[1] Of course the Sifrei, like the verse, also deals only with the construction of guardrails and thus supports only one aspect of Rav Natan - the application beyond the home. 

[2] See Me'iri (s.v. Chayav, Bayit) who infers this point.  This would be the basis for the Rambam's similar opinion (Rotzeach 11:4).  See also note 8. 

[3] See also Abayei (46a) who explains R. Eliezer's position quoted in the mishna (45b) as based on Rav Natan.  The other Tannaim, who (at least according the Rashi 45b s.v. Ela) disagree with R. Eliezer, might do so because of their rejection of Rav Natan's expansion of the verse.

[4] The Semak does not explicitly mention Rav Natan.  One could claim that although he himself believed in this distinction, he did not believe it to be the opinion of Rav Natan.  Compare also the Yere'im's discussion of the Lav (siman 310) to that of the aseh (siman 334).

[5] Emek Hanetziv (Netziv's commentary on the Sifrei) 'Min Hama'aka.'

[6] Shu"t Devar Avraham 1:37:25.  He proves his suggestion from the Rambam (Rotzeach 11:2) who describes the pit as 'bor be-chatzero.'  See also Kehillat Yaakov (Steipler) on our sugya who suggests a similar distinction.

[7] Klal 15:24.  See also Chazon Ish (Rotzeach 11:2-3) who uses this distinction to explain the Semag who distinguishes between the height of the railing needed for a porch and a pit.

[8] This distinction might also explain the Rambam's stress on life-threatening situations only when discussing the Lav (Sefer Hamitzvot Lo Ta'aseh 398) as opposed to when discussing the aseh (Aseh 184).  On the other hand, see Hilkhot Rotzeach where the Rambam seems to merge the two.

[9] See Ran (on Rif 15b s.v. Ve-af) who, assuming Tosafot's criteria, points out that even when constructed by the owner, the Lav applies at the time of the construction while the aseh becomes relevant only after the porch is fully constructed.