Beitzah, Chapter Two, Mishnah 9. In the previous mishnah we discussed grinding in a pepper mill on Yom Tov, and from here our mishnah turns to a different subject: the laws of tumah and taharah, and the status of the pepper mill and its parts.
The text of the Mishnah:
"Reichayim shel pilpelin temei'ah mishum sheloshah" - a pepper mill contains three different types of components, and each one of them has an element that causes it to be considered a vessel, meaning that it is susceptible to tumah.
The three components:
Because of a receptacle - the receptacle in which the pepper is placed is a container, and by its very definition it is susceptible to tumah. Even if it is made of wood, it is still a wooden vessel that can hold and contain something, and therefore it is considered susceptible to tumah.
Because of a metal vessel - the part that does the grinding is made of metal. And even if we are dealing with what we call a flat metal vessel, that is, a vessel that does not contain anything, since its function is to crush and grind and it is made of metal, it is considered tamei.
Because of a kli chivarah - the middle part of the pepper mill was a sort of sifter, like a mesh.
Why is the kli chivarah tamei?
Some understand that it is tamei because it resembles a receptacle, like the container part, even though it is not literally a receptacle.
Others understand that its tumah stems from a different reason: it resembles a woven vessel, because of the way its parts interlace with one another. This tumah is rabbinic - the Sages said that it should be tamei because it is like a woven vessel.
In summary: in this mishnah we learned that a pepper mill is susceptible to tumah on account of three components: its receptacle, which is a container that is susceptible to tumah even when made of wood; the metal grinding part, which is tamei even though it is a flat metal vessel; and the kli chivarah in the middle, regarding which there is a difference of opinion as to the reason for its tumah - whether because it resembles a receptacle, or because it resembles a woven vessel, and this by rabbinic law.