Keilim 5:5-6

Keilim 5:5

The extra clay on a homeowner’s oven is not susceptible to ritual impurity (because it serves no purpose) but that on a professional baker’s oven is susceptible because he leans his spit on it. Rabbi Yochanan HaSandlar says the reason it’s susceptible to impurity on a baker’s oven is because he bakes in it when circumstances require it. Similarly, the clay rim around a vat used by olive cookers is susceptible to ritual impurity but the one on a dyer’s vat isn’t.

Keilim 5:6

Let’s say that an oven was filled halfway with earth. The part below the earth is susceptible to ritual impurity through touching and the part above the earth is susceptible to ritual impurity through its airspace. Let’s say that a never-fired oven was placed over the mouth of a pit or a well and a stone was placed to keep it from falling in. Rabbi Yehuda says that if one could light a fire below (i.e., in the pit) that would heat the oven above, then it is susceptible to ritual impurity. The Sages say that an oven is susceptible to ritual impurity once it has been heated in any manner.