Kelim, Chapter Twenty-Six, Mishnah Five
1) The following hides are susceptible to midras uncleanness:
a) A hide which he intended to use as a rug,
b) A hide used as an apron,
c) A hide used as the lower covering of a bed,
d) A hide used by a donkey-driver,
e) A hide used by a flax-worker,
f) A hide used by a porter,
g) A hide used by a doctor,
h) A hide used for a crib,
i) A hide put over a child’s chest,
j) A hide for a cushion.
k) A hide for a covering.
i) All these are susceptible to midras uncleanness.
2) A hide for wrapping up combed wool and a hide worn by a wool-comber:
a) Rabbi Eliezer says it is susceptible to midras,
b) But the sages say that it is susceptible to corpse uncleanness only.
Section one: For a hide to be subject to midras uncleanness it must be either sat, laid or leaned upon. All of the following hides fit this criterion. I shall explain the ones that seem to require some explanation.
A hide used by a donkey-driver: While usually put over his clothing, sometimes he would sit on this hide.
A hide used by a flax-worker: Placed in front of the flax-worker to protect him while he beats the flax.
A hide used by a porter: The hide covers his shoulders.
A hide used by a doctor: As an apron.
A hide put over a child’s chest: Like a bib.
While the main use of these hides is not necessarily for sitting, leaning or lying down, they are sometimes used in this manner and therefore they are susceptible to midras impurity.
Section two: According to Rabbi Eliezer, the hide used to cover combed wool and the hide used to protect wool-worker are also susceptible to midras, because sometimes one might sit or lie on them. The sages disagree and say that these types of hides are not sat or laid upon and therefore are susceptible only to corpse impurity, which is true of all vessels.