Commentaire sur Oholot 4:1
מִגְדָּל שֶׁהוּא עוֹמֵד בָּאֲוִיר, טֻמְאָה בְתוֹכוֹ, כֵּלִים שֶׁבְּעָבְיוֹ טְהוֹרִים. טֻמְאָה בְעָבְיוֹ, כֵּלִים שֶׁבְּתוֹכוֹ טְהוֹרִים. רַבִּי יוֹסֵי אוֹמֵר, מֶחֱצָה לְמֶחֱצָה. הָיָה עוֹמֵד בְּתוֹךְ הַבַּיִת, טֻמְאָה בְתוֹכוֹ, הַבַּיִת טָמֵא. טֻמְאָה בַבַּיִת, מַה שֶּׁבְּתוֹכוֹ טָהוֹר, שֶׁדֶּרֶךְ הַטֻּמְאָה לָצֵאת וְאֵין דַּרְכָּהּ לְהִכָּנֵס. כֵּלִים שֶׁבֵּינוֹ לְבֵין הָאָרֶץ, שֶׁבֵּינוֹ לְבֵין הַכֹּתֶל, שֶׁבֵּינוֹ לְבֵין הַקּוֹרוֹת, אִם יֶשׁ שָׁם פּוֹתֵחַ טֶפַח, טְמֵאִין. וְאִם לָאו, טְהוֹרִין. טֻמְאָה שָׁם, הַבַּיִת טָמֵא:
Une armoire debout [à l'extérieur] en plein air: S'il y a des impuretés à l'intérieur, les récipients dans l'épaisseur [de ses murs] sont purs. S'il y a des impuretés dans son épaisseur, les récipients à l'intérieur [de l'armoire] sont purs. Le rabbin Yose dit: moitié-moitié. S'il se trouve à l'intérieur d'une maison: s'il y a des impuretés à l'intérieur [de l'armoire], la maison est impure; S'il y a de l'impureté dans la maison, ce qui est à l'intérieur [de l'armoire] est pur, car la manière de l'impureté est de sortir et sa manière n'est pas d'entrer. Des vaisseaux qui sont entre [l'armoire] et le sol, ou qui sont entre lui et le mur, ou qui sont entre lui et les poutres du toit: s'il y a là un espace pour la largeur des mains, ils sont impurs. Sinon, ils restent purs. S'il y a des impuretés là-bas, la maison devient impure.
Bartenura on Mishnah Oholot
English Explanation of Mishnah Oholot
When it is standing inside a house: If there is uncleanness inside [the cupboard], the house is unclean; If there is uncleanness in the house that which is within [the cupboard] remains clean, for the manner of uncleanness is to go out and not to go in.
Vessels which are between [the cupboard] and the ground, or between it and the wall, or between it and the roof-beams: If there is a space of one cubic handbreadth there, they become unclean. If not they remain clean.
If there is uncleanness there, the house becomes unclean.
Section one: The cupboard in our mishnah is large enough such that it doesn't receive impurity in itself. The cupboard is outside in the open air and not in the house.
If there is a source of impurity in the cupboard, and there are vessels in niches in the thickness of its walls, these vessels remain pure. These niches are not considered to be in the space of the cupboard. Similarly, if there is a source of impurity within the niches, the vessels inside the cupboard are pure.
Rabbi Yose disagrees. He divides these niches in half and says that the inner half is considered to be like the cupboard and the outer half is considered to be like the space outside the cupboard.
Section two: If the cupboard is within a house, then the impurity can escape the cupboard and go into the house (even if the cupboard is locked), but impurity from the house does not enter the cupboard (as long as the cupboard is closed). This is because of the rule that impurity escapes but does not enter.
Section three: This section describes a situation in which vessels are found in between the cupboard and the walls, floor or roof of the house, and there is a source of impurity in the house or in the cupboard. If there is a space that is at least 1 x 1 x 1 handbreadths, then the impurity goes in there through the fact that the house acts as an ohel. But if the space is smaller, the impurity does not enter, for impurity does not enter such small spaces.
However, if there is impurity in that space, then the house is impure because the impurity is inside the house. The cupboard is impure because impurity goes out but does not enter.