Kelim, Chapter Eight, Mishnah Four
1) A pot which was placed in an ovenif a sheretz was in the oven, the pot remains clean since an earthen vessel does not impart impurity to vessels.
2) If it contained dripping liquid, the latter contracts impurity and the pot also becomes unclean.
a) It is as if this one says, “That which made you unclean did not make me unclean, but you have made me unclean.”
Section one: The sheretz in the oven does not defile the pot because it is not in the air-space of the pot, but rather in the air-space of the oven. And the oven’s contact with the pot does not defile the pot because earthenware vessels do not defile other earthenware vessels.
Section two: If there is liquid dripping off the pot, it is defiled by the oven which was defiled by the sheretz. In turn this liquid causes the pot itself to become impure because liquids can defile earthenware vessels. The mishnah personifies a dialogue between the pot and the liquid (think Mrs. Potts in Beauty and the Beast). The pot says to the liquidthe oven which made you unclean didn’t directly make me unclean. But you, Mr. Liquid, you made me unclean!