Mishnat Hashavua’: Kelim 5:7

How does one purify an oven?

How to purify an oven that had become impure? Divide it into three sections, and then scrape the inner lining down to the ground. Rabbi Meir says that it is unnecessary to scrape the lining, and not to the ground, but rather just to reduce it within by four hand breadths. Rabbi Shimon says, he must separate [the three sections]. If [the oven] is divided in two parts, one large and the other small, the large part remains impure, but the small part is pure. If [the oven] is divided in three parts, one that is larger than the other two combined, the large part is impure, and the small ones are pure.


The final division of the Mishnah, Tohorot, deals with extremely arcane rules of ritual purity and impurity. The first and largest tractate, Kelim (utensils) examines the different levels of purity and impurity, how they affect various substances and are transmitted. When an earthen vessel is contaminated, the only way to purify it is to break it, so that it is no longer a functional vessel. Ovens in the Talmudic era were often made of stones set on the ground and coated with plaster inside. This Mishnah reviews how thoroughly the oven should be disassembled before being considered pure. If one section remained large enough to function as a separate oven, it apparently required further disassembly.


  1. If we can treat this oven as a metaphor for moral purity, what does it teach about the stages necessary for purification?
  2. This protocol for purification differs from that of kashering utensils, which are typically scoured and heated. What does the difference indicate about the separate concerns of purity and kashrut?

* Please Note: we inadvertently skipped tractate Kelim two weeks ago. We present it now, and will return to our regular order next week.