Negaim, Chapter 5, Mishnah 4. Our mishnah preserves a well known argument concerning one of the three simanei tumah of a nega in ohr habasar, the skin of the body. Some background is needed. A nega on the skin is declared tamei through any one of three simanim, each of which must appear inside a white patch measuring a gris, a baheres kagris. The first is se'ar lavan, a pair of hairs that had been black and which the discoloration turned white. The second is michyah, a square of healthy flesh sitting in the middle of the patch. The third is pisyon, the spreading of the nega when the first week of hesger concludes, or the second. The question our mishnah raises concerns se'ar lavan: what becomes of this siman when the baheres that produced it vanishes and afterward comes back?
The dispute
The dispute
The Mishnah's subject is "se'ar pakuda." Regarding it we are told that "Akavya ben Mahalalel m'tamei" while the Sages, "v'chachamim m'taharin," disagree. This is the great tanna about whom Chazal testified that the doors of the Azarah were never locked behind any Jew who equaled him in wisdom and in fear of Heaven. His ruling is that se'ar pakuda carries tumah, while the Chachamim declare it tahor.
The term itself is instructive. The Rav points out that pakuda stems from pikadon, an item handed over for safekeeping: the nega moved out and deposited something behind it for storage, and that deposit is the whitened hair.
The Mishnah's definition
The Mishnah's definition
The Mishnah now spells out what the term means: "Eizehu se'ar pakuda? Mi shehaysah bo baheres, uvah se'ar lavan." A man developed a baheres measuring a gris, and inside it a siman of tumah appeared: two hairs, formerly black, that the patch had whitened. Until this point we have a perfectly ordinary case of tumah. Then, however: "halchah habaheres v'hinichah l'se'ar lavan bimkomo, v'chazrah." The white patch itself faded away, while the white hair remained standing where it was, and subsequently the baheres came back.
That return is what the entire ruling rests upon. Even Akavya ben Mahalalel would concede that a solitary white hair with no nega surrounding it carries no tumah whatsoever, since a siman of tumah has to be situated within a baheres kagris. His position addresses only this sequence of events: the patch appeared first and demonstrated its potency by turning black hairs white; it then withdrew while those hairs stayed put; and finally the nega came back to the very same hairs, which were already standing there.
In such a case Akavya ben Mahalalel is m'tamei, and the Chachamim are m'taharin. The reasoning of the Chachamim is that the baheres kagris must both precede the white hair and continue to exist together with it. Once the baheres departs and only then returns, its return is treated as if the white hair came first and the nega afterward, and a white hair that preceded the nega is no siman at all. Therefore the man is tahor.
Rebbi Akiva's version
Rebbi Akiva's version
"Amar Rebbi Akiva: Modeh ani b'zeh shehu tahor." In this case Rebbi Akiva lines up with the Chachamim against Akavya ben Mahalalel: where the white patch disappeared completely and only later returned, the man is tahor. He then supplies a definition of his own: "Eizehu se'ar pakuda? Mi shehaysah bo baheres kagris, uvah shtei se'aros, v'halach mimenu k'chatzi gris v'hinicho, v'chazar." A baheres measuring a gris whitened two black hairs. Afterward only half a gris of that patch faded away, so the white hair was left standing within the portion where white still remained, the surviving half-gris; later the missing half returned.
In that case, Rebbi Akiva holds, the white hair is tamei. It was never left bare: it remained surrounded by baheres throughout, even though at one point the surrounding baheres was less than a full gris, and in the end the complete gris returned.
The Chachamim do not accept this construction either. In their view a full baheres kagris must come before the white hairs, be present together with them, and remain unbroken from start to finish. They therefore replied to him: "K'sheim shebitlu es divrei Akavya, af d'varecha einan m'kuyamin." Just as the ruling of Akavya ben Mahalalel was rejected in the case where the nega left completely, so too your position cannot be sustained. Here as well the metzora is tahor.