Ohalot, Chapter Thirteen, Mishnah Six
Today’s mishnah refers mostly to cases that are opposite of those found in yesterday’s mishnah. It lists things that do not reduce the area of the window.
1) The following do not reduce [the area of the window]:
a) Bone does not reduce [the area] for [other] bones;
b) Nor [corpse] flesh for [other] flesh;
2) Nor an olive-sized [portion] of a corpse;
3) Nor an olive-sized portion of carrion;
4) Nor a lentil-sized portion of reptile;
5) Nor an egg-sized portion of food;
6) Nor produce growing in the windows;
7) Nor a cobweb having no substance;
8) Nor the carcass of a clean bird which had been intended [for food];
9) Nor the carcass of an unclean bird which had been intended [for food] and had been rendered susceptible to uncleanness;
10) Nor warp and woof threads that have negaim;
11) Nor a brick from a bet haperas, the words of Rabbi Meir.
a) But the sages say: the brick can reduce, because the dust [of the bet haperas] is clean.
12) This is the general rule: what is clean reduces [the area], and what is unclean does not reduce it.
Section one: Since the substance found in the window is the same as is found in the house, they don’t reduce the area of the window.
Sections two-five: All of these are simply the opposite cases of those taught in mishnah five. There is a sufficient amount that it is susceptible to impurity.
Section six: In this case the produce grows directly out of the window and not just adjacent to the window, as it did in yesterday’s mishnah. Since one does not want to keep such produce, it doesn’t reduce the size of the window.
Sections seven-nine: The opposite of those cases found in yesterday’s mishnah.
Section ten: Negaim are what we might call “plagues” or some type of disease that infects cloth. There will be an entire tractate devoted to this subject. If the cloth has negaim, then it is impure and anything impure does not reduce the area of the window.
Section eleven: A bet haperas is a field that used to be used as a cemetery but was plowed over. The brick was made from the ground of such a field. According to Rabbi Meir, such a brick is impure and therefore it does not reduce the window. The other sages disagree because they hold that dust that comes from a bet haperas is clean.
Section twelve: This is the general rule that explains all of mishnayoth 5-6.