Negaim, Chapter 13, Mishnah 12. This is the closing mishnah of the perek, and it deals with a very practical problem: the metzora is a person, and a person wants to come to shul. May he? And if he comes, how do we protect everyone else from his tumah? Out of this mishnah emerges one of the fundamental differences between the tumah of a metzora and the tumah of a meis.
A Halachah That Grows Out of This Mishnah
The mishnah just before ours recorded a machlokes between Rebbi Shimon and the first, unnamed Tanna over how far a metzora spreads tumah when he walks into a place: does it rise all the way to the beams overhead, or does it stop at his four amos? Our mishnah takes up a further question in the same area, and the poskim extract from it a principle of wide application.
The Tiferes Yisrael sets the two tumos side by side in his introductory survey of the practical halachos at the start of Seder Taharos, the Mareh Kohen. Take a meis lying in a house. Even when a wall stands between the corpse and the objects that are still tahor, if there is a gap of one square tefach over the top of that wall linking the one room to the other, the two airspaces count as a single space by way of that gap, and the tumah travels across. A barrier is no obstacle to tumas meis once the air above it is shared by both sides.
With a metzora, matters work along completely different lines. Any time a partition ten tefachim tall stands between him and the area that is clean, whatever is on the other side keeps its taharah, and this holds true even when the air overhead is fully continuous and open from one side of the barrier to the other. Consider how low ten tefachim really is: something like forty inches, just past the waist of an average man. That is hardly a wall that closes anything in. Still, it does the job. The Tiferes Yisrael points to Perek Yud Gimmel, Mishnah Yud Beis as his proof text: our mishnah is where the halachah that a partition holds back a metzora's tumah begins.
Is the Mechitzah for Tumah or for Tefillah?
The Meleches Shlomo directs us to a teshuvah of the Mahari Isserlein, the author of Terumas HaDeshen. A note on locating it: it does not appear among the responsa printed at the beginning of the volume, but rather in the latter half, in the section called Pesakim, at siman tzadi hei. Mahari Isserlein belonged to the last generation of the Rishonim, a posek of the highest stature who stood in the tradition of the beis midrash of the Maharam of Rothenburg.
A questioner came to him having seen the din of our mishnah quoted in the Semag, the Sefer Mitzvos Gedolos, and he understood it to be a law of mechitzah on account of kedushas tefillah: the metzora needs a partition because of the sanctity of the place of prayer, and not because of tumah at all.
The Terumas HaDeshen replies that he possesses a peirush of the Ri mi'Simpont on all of Seder Taharos. He looked into it at Maseches Negaim, perek Yud Gimmel, and found the explanation of this mishnah there: the mechitzah is for tumah alone, nothing else. And he adds a proof from the mishnah adjacent to it, which distinguishes the tumah of a metzora from the tumah of a meis in several respects, in the matter of tzamid pasil and in the matter of keilim inside a bor or a dus that stand within the house. (What the Terumas HaDeshen refers to as the adjacent mishnah is, in our text, the continuation of this very same mishnah, as we will see in a moment.)
The Mishnah Itself
"Nichnas leveis hakeneses": should the metzora come into the beis hakeneses, the tzibbur must put up a partition for him, "osin lo mechitzah", of specified dimensions, "gevohah asarah tefachim al rochav arba amos", ten tefachim in height by four amos across. The assumption is that it surrounds him on every side, giving him a small enclosure of his own so that no one else contracts tumah from him.
Why specifically ten tefachim? The Rav explains that a barrier lower than that does not qualify in halachah as a mechitzah at all, and consequently has no power to spare the others from what the metzora conveys.
And why four amos? Corresponding to the four amos of tefillah. The meforshim offer several understandings of what those four amos are. Some say it is the space around a person who is davening, into which another may not come. Some say it is the room a person needs in order to sit and spread himself out while he davens. Some speak of the fact that in the days of the mishnah they would actually fall on their faces for tachanun, bipishut yadayim veraglayim, with hands and feet outstretched, and for that he needs four amos of floor. The Rav also offers a simpler reason: four amos is the shiur of a person's own place, as we find in Eiruvin, perek Mi Shehotzi'uhu. Wherever the halachah assigns a man his place, it gives him his four amos.
"Nichnas rishon veyotzei acharon." He enters first and leaves last. Now, we know the rule of tumah overes: tumah that is passing through, moving beneath a roof without stopping, does not render things tamei b'ohel while it travels. Why then must he come before everyone and leave after everyone? Because of a concern. If he were to walk in while the tzibbur is already assembled, or to leave while they are still there, cutting through the crowd, he might pause for a moment. The moment he pauses he has a moshav, a stopping place, and then he is metamei everyone under that roof b'ohel. It is not that walking through is forbidden in itself; it is that we do not rely on his never coming to a halt. Therefore he comes in before them and goes out after them.
What Protects Inside a House With a Negah
The mishnah continues: "Kol hamatzil tzamid pasil b'ohel hameis, matzil tzamid pasil b'veis hamenuga; vechol hamatzil mechuseh b'ohel hameis, matzil mechuseh b'veis hamenuga, divrei Rebbi Meir."
The rules being invoked here are taken from Maseches Ohalos. An earthenware vessel has a unique capacity: seal its opening tightly, a tzamid pasil, and its contents escape the tumah of an ohel hameis. Other things require no more than a lid laid over them: a pit dug out for water within the dwelling, or a dus, a similar reservoir put together from masonry and built up as a structure. Cover such a receptacle before the corpse is brought inside, and whatever it holds stays tahor.
Rebbi Meir holds that the beis hamenuga is exactly parallel. Whatever saves by means of tzamid pasil in an ohel hameis saves by means of tzamid pasil in a house afflicted with a negah, and whatever saves by means of a covering in an ohel hameis saves by means of a covering in a house with a negah.
Rebbi Yosei disagrees, and his position follows the line we have already seen, that the tumah of a metzora is lighter than the tumah of a meis. He lowers the requirement by one step in each case: "Kol hamatzil tzamid pasil b'ohel hameis, matzil mechuseh." Whatever requires a sealed tzamid pasil by tumas meis needs only a covering in the house of the negah. "Vechol hamatzil mechuseh b'ohel hameis, afilu meguleh b'veis hamenuga tahor." Whatever needs only a covering by tumas meis, such as the bor or the built dus, remains tahor in the house of the negah even standing open and uncovered.
The Rav, and the Rambam in the Yad, pasken like Rebbi Yosei: we are more lenient regarding protection from the tumah of a house with a negah than we are regarding protection from the tumah of a meis in an ohel. Whatever demanded a sealed tzamid pasil by a meis is saved in a beis menuga by a plain covering, and whatever demanded a covering by a meis needs no covering at all in a beis menuga. And with that we reach the close of Perek Yud Gimmel.