Mikvaos, Chapter 2, Mishnah 2. This mishnah belongs to the group of mishnayos dealing with doubts surrounding a tevilah: the tumah itself is certain, and the only question is whether the immersion accomplished anything. Here the Mishnah adds two crucial refinements: when a doubt is strong enough that we treat it as though it were a certainty, and how everything changes when the tumah in question is only mid'rabbanan.
The Background Rule of Reshus Hayachid and Reshus Harabim
As is well known from Shas and the poskim, a safeik tumah that arises in a reshus hayachid, a private domain, is ruled tamei, while a safeik tumah that arises in a reshus harabim, a public domain, is ruled tahor. Our mishnah teaches that there are situations in which the doubt is so heavily weighted toward tumah that we effectively remove the doubt altogether and treat the case as a certainty. In such a situation, even a reshus harabim will not save it.
A Mikveh That Was Measured and Later Found Lacking
"Mikveh shenimdad v'nimtza chaseir." A mikveh was measured and found to contain the full forty se'ah. People used it. Then, two weeks or three weeks later, it was measured again and found to hold less than forty se'ah.
Here is the Mishnah's verdict: "Kol hateharos shena'asu al gavav," all the purifications carried out in it, "bein bi'reshus hayachid bein bi'reshus harabim, t'meios." Anything that was toveled in that water in the stretch of time between the first measuring and the second gains nothing: keilim whose tumah had been established, or a person whose tumah had been established, come out of the water exactly as they went in, still tamei. And the domain makes no difference at all; the ruling is identical for a private location and for a public one.
Why? Because here we have what Chazal call tartei l'rei'usa, two factors pulling in the direction of tumah. First, the gavra or the keli carries a chezkas tumah: its last established status was tamei. Second, mikveh chaseir lifanecha: the mikveh standing before us right now is lacking. These two considerations join forces and outweigh both the leniency of a safeik tumah in a reshus harabim and the fact that this mikveh had once been properly measured.
Only for Tumah Chamurah
"Bameh devarim amurim?" The Tanna Kamma limits the rule. We apply tartei l'rei'usa only to tumah chamurah, a tumah whose source is d'oraisa, a status of tamei established by the Torah itself.
"Aval b'tumah kalah": but where the tumah is only mid'rabbanan, the halacha is different. The mishnah lists the examples:
- "Ochel ochlin t'meiyim": a person who ate foods that were tamei. The Torah itself does not make such a person tamei; it is the Chachamim who imposed this status on him.
- "O shosah mashkin t'meiyim": or he swallowed liquids that were tamei.
- Or "ba rosho v'rubo" into "mayim she'uvin," his head together with most of his body entered water that had been drawn into a vessel. This status too rests on a rabbinic decree.
- Or the reverse: "shenaflu al rosho v'rubo" a quantity of "gimmel lugin mayim she'uvin," three lugin of drawn water landed on his head and on the larger part of his body.
All of these are rabbinic tumos, which disqualify a person from eating terumah.
"V'yarad litbol": this man went down to immerse, and now uncertainties present themselves. "Safeik taval safeik lo taval," it is unclear whether the tevilah actually took place. Or the tevilah is not in question at all, yet we do not know the volume of the water: a doubt whether "yesh bo arbaim se'ah," the mikveh held the required forty se'ah, or "ein bo," it did not. Or there stood before him two mikvaos, one valid and one deficient, "v'eino yodei'a b'eizeh meihen taval," and he cannot tell which one he used.
To every one of these questions the Tanna Kamma responds "sfeiko tahor." Granted, the last status established for this man was tumah; nevertheless, since the whole tumah exists only by rabbinic authority, the uncertainty amounts to no more than a safeik in a d'rabbanan matter, and such a safeik is resolved leniently. The mikveh that was measured and afterward discovered to be short falls under the identical principle: a person who immersed there solely to rid himself of a rabbinic tumah emerges tahor.
The Opinion of Rebbi Yosei
"Rebbi Yosei m'tamei." Rebbi Yosei disagrees and rules that the person remains tamei. His reasoning is stated in the mishnah: "Kol davar shehu b'chezkas tumah l'olam hu b'psulo ad sheyeida shetahar." Anything that carries an established status of tumah remains in its state of disqualification forever, until one knows with certainty that it has become tahor. According to Rebbi Yosei, it makes no difference that this is merely a tumah kalah of rabbinic origin. Once there is a chezkas tumah, a doubt cannot lift it.
The Limit of Rebbi Yosei's Stringency
"Aval sfeiko l'hitamei o l'tamei." There is a different kind of doubt entirely, and here even Rebbi Yosei is lenient. If the question is whether the person became tamei in the first place, meaning there is a doubt whether he ever came into contact with something tamei, or if the question is whether he transmitted his tumah onward to another object that he may have touched, then in a matter of d'rabbanan the ruling is tahor.
The difference is fundamental. In those cases there was never an established status of tumah to begin with; on the contrary, the person or the object involved carries a chezkas taharah. Rebbi Yosei's stringency applies only where a chezkas tumah has already taken hold and we are asking whether it was removed, not where we are asking whether it ever arrived.