Kelim, Chapter Nineteen, Mishnah Nine
1) A box whose opening is at the side is susceptible to both midras uncleanness and corpse uncleanness.
2) Rabbi Yose said: When does this apply? When it is less than ten handbreadths in height or when it does not have a rim one handbreadth deep.
3) If it was damaged above it is still susceptible to corpse uncleanness.
4) If it was damaged below:
a) Rabbi Meir rules that it is susceptible to uncleanness.
b) But the sages rule that it is clean because if the primary function ceases the secondary one also ceases.
Section one: Today’s mishnah discusses a box whose opening is at the side. Since this box can be sat upon it is susceptible to midras uncleanness. It is also susceptible to other types of impurity, including corpse impurity.
Section two: Rabbi Yose says that it is susceptible to midras impurity only if it is less than ten handbreadths high or does not have a rim of at least a handbreadth. A high box with a rim will not be sat upon, and therefore it is not susceptible to midras. But a low box might be sat upon, with or without a rim.
Section three: If it was damaged above, it cannot be sat upon so it is no longer susceptible to midras. But it is still usable as a box, so it is susceptible to corpse uncleanness.
Section four: If it is damaged below, it can be sat upon, but it cannot be used for storage, which is its main purpose. Rabbi Meir rules that since it can still be sat upon, it is susceptible to midras impurity. The sages disagree. They hold that if a vessel cannot be used in its primary function, in this case storing, it is not susceptible due to its secondary function, sitting. Therefore, the box is completely clean.