Kelim, Chapter Two, Mishnah Three
In our mishnah we learn that earthenware vessels are susceptible to impurity only if they have an “inner part” that is made to receive something.
1) The following are not susceptible to impurity among earthen vessels:
a) A tray without a rim,
b) A broken incense-pan,
c) A pierced pan for roasting corn,
d) Gutters even if they are bent and even if they have some form of receptacle,
e) A cooking vessel that was turned into a bread-basket cover,
f) A bucket that was turned into a cover for grapes,
g) A barrel used for swimmers,
h) A small jar fixed to the sides of a ladle,
i) A bed, a stool, a bench, a table, a ship, and an earthen lamp, behold these are no susceptible to impurity.
2) The following is a general rule: any among earthen vessels that has no inner part is not susceptible to impurity on its outer sides.
Section one: The vessels listed in this section cannot become impure because they do not have any “inner part,” which is made to accept things. Some of these should be understandable, but I will make an attempt to explain some of the others.
Gutters are not meant to hold the rain or other things and therefore they can’t be defiled.
The cooking vessel does have a receptacle, but since they changed it to be used as a cover for grapes which does not “receive” things, it is not susceptible to impurity.
The fact that the barrel holds a person does not seem sufficient to consider it a vessel that receives.
The little jar fixed to the sides of the ladle has a receptacle, but it is not used to put things in it. Therefore, it is not susceptible to impurity.
Section two: This is the general rule. An earthenware vessel that does not have an “inner part” cannot become impure by having something touch it on the outside. In contrast, vessels made of wood etc., can become impure even if they do not have an inner part. If they are made to “receive” something, such as a tray, then they are impure even though they do not have an “inner part.”