Keilim, Chapter 27, Mishnah 1. With this mishnah we begin a series of perakim devoted to the tum'ah of begged, cloth. When the Mishnah speaks of cloth it means fabric whose threads are woven together, whether the material is wool taken from sheep, fibers that come from plants, or silk. Felt, although its fibers are pressed rather than woven, is also treated as a kind of cloth.
The mishnah opens by ranking five materials according to how many different ways each one can be drawn into tum'ah: "habegged mitame mishum chamishah shemot," cloth becomes tameh under five headings; "hasak mishum arba'ah," sackcloth under four; "ha'or mishum sheloshah," leather under three; "ha'etz mishum shenayim," wood under two; "uchli cheres mishum echad," and an earthenware utensil under one alone. The mishnah then works through the list, and we will follow it, beginning from the bottom of the ladder and climbing upward.
Earthenware: only as a container
Vessels of clay have only a single avenue into tum'ah, and the mishnah names it: "mishum kli kibul," by virtue of holding contents. Unless the clay was formed with a hollow capable of containing something, it does not qualify as a utensil for this discussion at all. The mishnah states the principle sharply, speaking of cheres: "kol she'ein lo toch," whatever lacks an interior, "ein lo achorayim," has no exterior either. It is obviously not denying that such a piece of pottery has a physical back; it is denying that the back carries any halachic weight. Clay that contains nothing lies altogether beyond the reach of tum'ah, so when something tameh touches its outer surface, the pottery is left exactly as it was.
Wood: a container and a seat
Wood, the mishnah continues, is "musaf alav," it has something added to it: beyond the one route open to clay, a wooden article can be drawn into tum'ah in a second way as well, "mishum moshav." A moshav is anything a person settles his weight upon, a bench or a bed frame, and in that capacity wood takes on tum'ah even when nothing whatever is held inside it.
The mishnah gives a second illustration of wood's broader susceptibility: "vechen tavla she'ein lah lizbeiz," a flat tray with no rim running around its edge. Such a tray cannot serve as a container, since there is nothing to keep its contents from sliding off. Nevertheless, "bichli etz teme'ah, uvichli cheres tehorah." Made of wood it can become tameh, because even without walls it still has the function of bearing objects placed upon it. Made of earthenware it remains tahor, for earthenware, as we have seen, must actually contain in order to be susceptible. In short: earthenware, only as a receptacle; wood, as a receptacle and also as something that holds either objects or the weight of a person.
Leather: also as a tent
Leather occupies the next rung, above wood and therefore above clay too. To all the headings already listed the mishnah adds one more for or: "mishum ohalim," on account of tents. A hide stretched as part of the covering spread over a corpse contracts tum'ah precisely in its role as an ohel.
Sackcloth: also as a woven item
Sackcloth climbs one step higher still, carrying a fourth heading alongside leather's three: for sak the mishnah adds the category of "arig," a woven article. A comparison brings out the distinction. Slice a hide into narrow strips and weave them together, and the product has forfeited its standing as a utensil; tum'ah will not attach to it on that account. With sackcloth the result is the opposite: cut it into strips, weave those strips back into a fabric, and what you hold is still a kli and remains susceptible.
Cloth: even three by three
At the head of the list stands begged, which bears a fifth heading beyond the four of sackcloth: for cloth the mishnah adds "shalosh al shalosh," three by three. A swatch of fabric measuring three etzba'ot in each direction is already liable to tum'ah, tiny though it is. Every other material on the list must first amount to a real utensil, with size and purpose, before tum'ah can rest upon it, whereas cloth is caught already at a mere three fingerbreadths square.
The mishnah has thus laid out a graded ladder: earthenware at the bottom with a single avenue of susceptibility, and cloth at the top with five, each material inheriting the categories of the one below it and adding one of its own. This framework will guide us through the perakim that follow.