Keilim, Chapter 24, Mishnah 14. This chapter runs through a long series of utensils, each one divided into three categories: an item that can receive the severe tum'ah of midras (the tum'ah contracted when someone who is tamei sits, leans or lies upon an object made for sitting or lying), an item that cannot receive midras but can still become tamei through contact with a corpse, and an item that remains tahor from every form of tum'ah. Our mishnah applies that same threefold division to cloths.
Our mishnah begins with a heading for what follows: "shalosh mitpachot hen", meaning that cloths fall into three separate halachic groups, and the mishnah now spells out the rule governing each of them.
The hand towel
The hand towel
The first case is "shel yadayim, teme'ah midras": a towel meant for drying one's hands is subject to tum'at midras. How can a towel count as an object made for lying? Because people do in fact spread themselves out on such a cloth and doze on it, treating it for the moment like bedding, and this second use sits perfectly well alongside the first. Someone stretched out asleep on the cloth is not looking to dry anything just then, so neither purpose interferes with the other. The cloth is therefore truly available for lying, and midras applies to it.
The cloth for the sefarim
The cloth for the sefarim
Next comes "shel sefarim, teme'ah tum'at met": a wrapper made to protect a Sefer Torah is susceptible to the tum'ah of a corpse. One might have expected it to be free of tum'ah entirely, for an object whose sole purpose is to attend to another object rather than to a human being never enters the system of tum'ah at all, and this wrapper looks like it exists purely for the Sefer. In reality, though, it renders a service to people too: whoever read from the scroll would tuck his hands into the wrapping to warm them. Since it operates as a keli that benefits human beings, it is fit to receive tum'ah, and corpse tum'ah takes hold of it. Midras it escapes, because no one lies or sits on such a covering.
The shroud and the cover for the Levi'im's instruments
The shroud and the cover for the Levi'im's instruments
The final clause groups two items together: "shel tachrich", the sheet in which a body is wrapped for burial, and "shel nivlei benei Levi", the wrapping placed over the harps of the Levi'im. Concerning both the mishnah rules "tehorah mikelum": no category of tum'ah reaches them. The burial sheet attends to a body that is no longer a living person, and the wrapping over the harps attends to the instruments and not to any human being. On top of that, neither cloth has a beit kibul, a hollow that would give it the status of a vessel. With no receptacle and no service rendered to a living person, they fall entirely outside the framework of tum'ah.
The mishnah thus lays out the full range in a single line: the towel, which people rest upon, carries the severe tum'ah of midras; the Torah cover, which warms the reader's hands, is a keli that serves people and so receives corpse tum'ah though not midras; and the shroud and the instrument cover, which serve no living person and hold nothing, remain tahor from everything.