Mikvaos, Chapter 9, Mishnah 2. Our perek is occupied with the laws of immersion and, in particular, with chatzitzah: something interposing itself so that the mikveh water never reaches the skin of the person or the surface of the utensil being toiveled. The pasuk states, "verachatz es besaro bamayim vetaher," that he shall wash his flesh in the water and become tahor, and Chazal learn from this, in Maseches Sukkah on daf vov, amud alef, that no item may stand as a chotzeitz keeping the water away from the one immersing. Mishnah 2 carries forward the catalogue of such barriers. Where the previous discussion involved threads and straps tied on the body, the focus now shifts to matter that adheres to the skin, sticks in the hair, or coats a vessel.
One important caveat belongs at the outset. Chatzitzah is a broad and intricate topic with a great many fine distinctions, and nothing practical should ever be decided from the words of the mishnah by themselves. A real question in this area belongs before a rav who has genuine mastery of the subject, a posek fluent in these halachos who is equipped to rule on it. What follows is the mishnah at its simple, straightforward level.
The list of the Mishnah
The Mishnah begins its enumeration with "kilkei halev vehazakan," clumps of hair on the chest or in the beard that have become so tangled and matted together that water cannot work its way through them. Next, "uveis hasesarim ba'ishah," the concealed areas of a woman's body. Then "lifluf shechutz la'ayin," a discharge of the eye that has dried and hardened on the outer side of the eye. Following that, the Mishnah lists "vegeled shechutz lamakkah," the crust of dried blood that forms over a wound and sits on the surface of the skin, and "vehartiyah she'alehah," a plaster or dressing laid on top of that wound.
The list continues: "veseraf hayaveish," dried sap or hardened resin; "vegildei tzo'ah she'al besaro," crusts of filth on one's skin; "uvatzeik shetachas hatziporen," dough that became lodged beneath a fingernail; "vehamilmulim," and "vetit hayaven," and "vetit hayotzerim," and "vegis yevani." All of these interpose between the water and the body and are a chatzitzah. The last several items are types of clay and earth, and the Mishnah now goes on to define them.
Defining the clays
"Eizehu tit hayaven?" Which clay does the Mishnah intend by the term tit hayaven? Its answer: "zeh tit haboros," the sludge that settles at the bottom of pits and wells. As support, the Mishnah brings a pasuk, in which Dovid Hamelech says that Hashem lifted him "mibor sha'on," from a pit of tumult, "mitit hayaven," out of the miry clay. Since Scripture itself joins this clay together with the pit, that is precisely the mud our Mishnah is speaking about.
"Tit hayotzerim kemashma'o," potter's clay means exactly what it sounds like: the clay that the potters worked with in manufacturing their earthenware vessels.
Here the Mishnah records a dissenting view: "Rabbi Yose metaher beshel yotzerin umetamei beshel mareikah." Rabbi Yose holds that the potter's clay does not form a chatzitzah, while the type known as mareikah does form a chatzitzah and leaves the immersion invalid.
"Vegis yevani," the road clay, is defined by the Mishnah as "eilu yesodos haderachim," the clay of the roadbeds, the packed earth of the roadside foundations.
Immersing in clay, and immersing objects
Regarding all these types of clay the Mishnah teaches, "she'ein tovelin bahen velo matbilin osam." Even when such clay is somewhat liquid and loose, a person may not immerse himself in it, for it does not have the status of water, and one may not immerse utensils in it either.
"Ush'ar kol hatit, matbilin bo keshehu lach." Other kinds of mud and earth are different: one may immerse in them while they are moist and fluid enough to be treated as water.
Two everyday cases round off the mishnah. First, "velo yitbol ba'avak she'al raglav": one should not go down to toivel while dirt is still caked onto his feet, because that layer separates his skin from the water. Second, "lo yatbil es hakumkum bapecha'im": a kettle blackened with soot may not be toiveled in that condition, "ela im kein shifshef," only after he has scrubbed the soot away.
The theme running through the whole mishnah is a single one: tevilah requires the water to touch the body or the vessel directly, and whatever has dried, hardened, matted or caked onto the surface must be removed first. And once again, these are matters for a rav who is expert in the halachos of chatzitzah, and we have learned the mishnah here only at its plain level.