An oven that was filled with earth up to its midpoint: [The area] from the earth and downward contracts tumah via contact; [the area] from the earth and upward contracts tumah via airspace. [If] one placed [an oven] over the mouth of a pit or over the mouth of a cistern and placed a stone there, R’ Yehudah says: If he lights [a fire] below and [the oven] is heated above, it is tamei. But the Sages say: Since in any event [the oven] was heated, it is tamei.

An oven of stone or of metal is tahor, but [the metal oven] is tamei as a metal utensil. [If] it developed a hole [or] became damaged [or] cracked [and] one made a [clay] coating for it or a supplement of clay, it is tamei. How large must the hole be? [Large] enough for the flame to pass through. And the same applies to a stove. A stove of stone or of metal is tahor, but [the metal stove] is tamei as a metal utensil. [If] it developed a hole [or] became damaged [or] cracked [and] one made feet for it, it is tamei. If one plastered it with clay, whether on the inside or on the outside, it is tahor. R’ Yehudah says: On the inside it is tamei, but on the outside it is tahor.