Kelim, Chapter Three, Mishnah Six
1) As to dog’s tooth which which they line large jars: anything that touches it becomes unclean.
2) The plug of a jar is not regarded as connected.
3) That which touches the lining of an oven is unclean.
Section one: Dog’s tooth is a type of grass that was used to line jars. If the large jar becomes defiled, then the grass is defiled as well. If food or liquids then touch the lining they too are impure.
Section two: The jar’s impurity does not affect the plug of the jar because the plug is meant to be removed.
Section three: The lining of an earthenware oven is an integral part of the oven. Therefore, if the oven becomes impure the lining is impure as well and it will subsequently cause food or drink that comes into contact with it to become impure.