On Kiddushin 41b, the Gemara attempts several times to find a Binyan Av to teach that Shlucho Shel Adam K'Moso. In the end, the Gemara learns this principle from Gerushin and Korban Pesach and concludes that this Binyan Av works to teach that Shlucho Shel Adam K'Moso for Terumah and, presumably, for the whole Torah.
One Daf later, on 42b, the Gemara says that we cannot derive Ein Shaliach L'Dvar Avera from Meila because we learn the same principle from Shelichus Yad and therefore, these are Shnei Kesuvim Habaim K'Echad and Ein Melamdim, we cannot use them as a Binyan Av.
The question is what is the difference between these two situations, i.e. under what circumstances do we say that we can have a Binyan Av based on two Pesukim and when do we say that they are Shnei Kesuvim HaBaim K'Echad and we cannot make a Binyan Av?
Thank You.
Baruch Robinson, Chicago, Illinois, USA
(Please forgive the delay in response. Technical problems prevented the mailing of a number of responses.)
This is a very good question and really requires further study. I have not yet found any Mefarshim who discuss this.
I have two suggestions (the second one I came up with after the first, and I prefer it).
1. I suggest that it depends on what logic would state if we did not have a verse.
a. Since it is logical that Shelucho Shel Adam Kemoso, it is not necessary to have a lot of verses to teach this, and if we have two verses it is possible to learn that it applies to the entire Torah from these two.
In contrast, logic suggests that Ein Shali'ach l'Dvar Aveirah, so if we have only two verses it makes sense to say that we cannot learn from these two to the entire Torah.
b. I will explain a bit more. Tosfos in Kidushin (35a, DH Ela) writes that since two verses cannot teach for the rest of the Torah, it follows that these two verses teach that this Halachah applies only for these two verses and not for anything else. The reasoning behind this is that if the Torah would have wanted a certain law to apply always, then it would have been sufficient to write it in one verse and this would have automatically meant that this law applies everywhere. The reason why the Torah writes the law in two verses is to teach that the law applies only in these two cases and nowhere else.
c. To apply this in practical terms, we now understand what we can learn from Shelichus Yad and Me'ilah (in Kidushin 42b). Logic suggests that Ein Shali'ach l'Dvar Aveirah, based on the Sevara of "Divrei ha'Rav v'Divrei ha'Talmid Divrei Mi Shom'im" (42b) (one should have listened to Hash-m and not to the Shali'ach who told him to do an Aveirah). It follows that when the Torah states that for Shelichus Yad and Me'ilah there is a Shali'ach l'Dvar Aveirah, this means (according to Tosfos in Kidushin 35a) that only for these two Halachos does the latter rule apply, while for all other Halachos in in the Torah the rule is Ein Shali'ach l'Dvar Aveirah.
d. In contrast, when we come to learn that there is such a Din in the Torah as Shelichus, logic tells us that there should be. It makes sense that a person can ask someone else to perform a task for him. Hence, when the Gemara states that it would be possible to learn Shelichus from Gerushin and Korban Pesach alone, the Gemara is saying that it is sufficient to have these two verses and it is not necessary to look elsewhere for further sources, because we know already that we have a sufficient proof that there is such a thing as Shelichus.
e. For Shelichus, logic states that it should work, but if we had only one source, Gerushin or Korban Pesach, we might have said that there is not sufficient proof from either one to show that Shelichus applies for all situations in the Torah. If we would not have had Gerushin, we would have said that Shelichus is strong enough only for Dinim that can be achieved by thought alone. If we would not have had Korban Pesach, we would have said that Shelichus cannot work for holy matters. Once we have both Gerushin and Korban Pesach, all the objections have been removed, and we revert to the original "independant logic" ("Sevara Chitzonah") that Shelichus applies everywhere.
2. The following is what I believe a better and more accurate answer to your question.
a. The main point is that if it is possible to derive a Halachah from just one verse, then this is certainly preferable. This would be a "Binyan Av mi'Kasuv Echad," which is one of the thirteen principles by which the Torah is expounded (as recorded in the Beraisa of Rebbi Yishmael and which is printed in the Siddur in the morning prayers). This is why the Gemara states here (41b), "Chada mi'Chada Lo Asya" -- one Din cannot be derived from merely one other Din, which implies that if it would have been possible to learn from only one verse then this would have been the best option. This is because it would have been possible to learn from one verse to every other place in the Torah, had there been no Pircha on this way of learning.
b. So it is only because it is impossible to learn from one verse that we need to resort to learning from two verses. However, in such a case it follows automatically that the principle of "Shnei Kesuvim ha'Ba'in k'Echad Ein Melamdim" does not apply. This is because the reason why two verses cannot teach for the rest of the Torah is that it is always preferable, if possible, to derive from one verse, as we wrote above. If the Torah could have taught the law in one verse but nevertheless chose to teach the law in two verses, the reason must be that the Torah specifically wants us not to apply the law to the rest of the Torah. The fact that the Torah gave us two verses proves that the Torah wants to limit this law only to the two chosen Dinim and not to every Din of the Torah.
c. The above applies only if it would have been possible to learn from one verse. If, for some reason, it is impossible to learn from one verse, we no longer can say that the reason why the Torah teaches the law in two verses is in order to limit the law specifically to these two verses. Therefore, it follows that if we say "Chada mi'Chada Lo Asya," it is no longer possible to say "Shnei Kesuvim ha'Ba'in k'Echad Ein Melamdim," because we no longer have a proof that the Torah wants to limit the law to only two subjects.
d. This principle is illustrated in Bava Kama 5a, where the Gemara explains why the first Mishnah in Bava Kama needs to enumerate different kinds of damaging agents. Why does the Torah say both "Shor" and "Mav'eh"? The Gemara (end of 5a) explains that the Mishnah is asking why the Torah did not write just one type of damager, from we would have derived all other types of damagers. The Mishnah then explains why it is not sufficient to write only one. The Har Tzvi (Zevachim 50a) explains that if it would have been possible to learn from one verse, then the Gemara would not have asked, "Teisi Chada m'Tarti"; it would not have been possible to learn from two because, on the contrary, we would have said "Shnei Kesuvim ha'Ba'in k'Echad Ein Melamdim."
e. Now we can apply the above ideas to the Gemara here in Kidushin. The Gemara (41a-b) always attempts, where possible, to derive Shelichus from only one verse. It is only when the Gemara determines that this is not possible that it suggests that it should be derived from two verses. However, it is not possible now to say that these two verses are "Ein Melamdim" because there is a good reason for why the Torah states two verses, and thus we cannot say that the reason why the Torah states these two verses is to exclude everthing else.
f. However, when it comes to Ein Shali'ach l'Dvar Aveirah, the situation is different. It would have sufficed to teach this principle in the verse of Me'ilah, and we would have derived it from Meilah to the rest of the Torah. The fact that the Torah teaches it also in the verse of Shelichus Yad tells us that it applies only in Me'ilah and Shelichus Yad, but not anywhere else in the Torah.
(I think if you look carefully at Tosfos in Yoma 42b, DH l'Mishemeres, near the beginning (especially the words "d'Lo Tzerichi"), you will find support for what I have written.)
3. I later posed your question to a Gadol and he replied tersely and rather cryptically: "Kan Shnei Minim" (literally, "Here, they are two species").
I understand that this means something similar to what I wrote above in #2. This principle -- that we cannot learn from two verses -- applies only when these are two similar verses. However, when there is a special reason for why only one of these verses would not have suffices to teach the law for the rest of the Torah, then it is possible to learn from these two verses. In other words, in such a case these two verses are "two different species" -- they are two different kinds of verses, and thus it is not possible to learn from one of them alone, and the rule of "Ein Melamdim" does not apply.
Dovid Bloom
I posed your question to a Gadol and he replied tersely and rather crypticly:-
"Kan Shnei Mimim", literally "Here they are 2 species".
I understand that this means something similar to what I wrote above in the second reply. The principle that we cannot learn from 2 verses only applies if these are 2 similar verses. However if there is a special reason why only one of these verses would not have been sufficient to teach us for the rest of the Torah, then it is possible to learn from these 2 verses. In other words in such a case these 2 verses are "2 different species" - they are 2 different kinds of verses and therefore it is not possible to learn from one of them alone, so in this case it is possible to learn from 2 verses.
Dovid Bloom