Rambam - 1 Chapter a Day

In Talmudic times, it was common for there to be a sun light in the middle of a house. Needless to say, the aperture must be open to the air, without a covering over it [the Rambam’s Commentary to the Mishnah (Ohalot 10:1)].

I.e., a corpse, a portion of its flesh, its bones, or the like.

Thus if there are any keilim placed there, they do not become impure.

Because it is under the same ohel as the source of impurity.

None of the keilim or people in the house become impure, because the impurity is considered as being under the open space and not in the house (ibid.).

Because it is considered as if the entire impurity is under the roof of the house.

And similarly, it is considered as if the entire impurity is under the aperture. The rationale is that, since the impurity is a single, undivided entity, we consider it as such and view it as being under both the house and the aperture (ibid.).
The Ra’avad and the Kessef Mishneh suggest amending the Rambam’s text and having it read “the space above the impurity” rather than “the space below the aperture,” because there is no reason to deem an entity in the space of the aperture impure if it is not positioned over the impurity. The authentic manuscripts and early printings of the Mishneh Torah corroborate the wording of the standard printed text.

Depending on whether the source of impurity is flesh, bones, or other substances, the size of the minimum measure varies, as explained in Chapters 1 and 2.

Because the entire house is considered as enclosed and containing impurity.

It is as if there is no aperture there (ibid.).

i.e., the one who placed his foot over the aperture.

Which renders him impure.

This is speaking about a situation where the aperture is less than a handbreadth by a handbreadth in size.

Although impurity does not depart through an aperture less than a handbreadth by a handbreadth, that is true only when the person is not standing over the impurity itself. In such an instance, he is impure, regardless of the size of the aperture.

Generally, we follow the principle that a person’s body does not intervene in the face of ritual impurity (Chapter 12, Halachah 1). Nevertheless, in this instance, the person’s foot is not considered as an independent entity, but as part of the roof.

In this instance, the impurity becomes part of the roof of the house, as it were, and everything in the house is considered as under the impurity.

That is not under the aperture.

Whether in the house or the loft.

Because the impurity ascends through the apertures.

When the impure object was placed on the aperture above the loft, everything is impure, because everything is contained in one shelter. When the impurity is placed on the aperture of the house, it closes the house and causes it to contract impurity. Afterwards, since it does not intervene in the face of impurity, it also conveys impurity to the loft.

The pure object intervenes in the face of ritual impurity and thus causes the loft to be considered as distinct from the house.

For then the two are considered as one single entity, through which the impurity diffuses.

For the pure object intervenes and confines the impurity to the house and loft.

That was less than a handbreadth by a handbreadth.

As explained in Halachah 1. The Kessef Mishneh explains that this is speaking about an instance where the impurity was there before the aperture was closed. If, however, the aperture was closed first different rules apply, as evident from a comparison to Halachah 1.

Because the impurity will not extend from the house to the loft if the aperture is less than a handbreadth by a handbreadth.

I.e., due to wind, a falling object, or the like.

As stated in Chapter 14, Halachah 2.

In his Commentary to the Mishnah (Ohalot 12:4), the Rambam points to Deuteronomy 3:11 as the source for this translation.

And the impurity can spread, because the aperture is a handbreadth by a handbreadth.

Because the impurity does not spread if there is less than a handbreadth by a handbreadth of open space.
The Kessef Mishneh questions why this law is different than the case mentioned in the previous halachah when the aperture is covered by an article that is susceptible to ritual impurity, in which instance, the Rambam ruled that the impurity was extended. In resolution, the Kessef Mishneh explains that here, the leg fills the hole and makes the ceiling a continuous entity, while in the previous halachah, the object is merely covering the aperture.

In his Commentary to the Mishnah (loc. cit.), the Rambam emphasizes that the bed also becomes impure and, indeed, acts as a source of impurity, causing everything that touches it to also contract impurity.

The Kessef Mishneh states that this is speaking about an instance in which the impurity was placed under the aperture and was placed there before the foot of the bed closed it.

See the conclusion of the previous halachah.

I.e., the pot was positioned upright and there was less than a handbreadth of open space between the impurity and the pot.

For example, the pot was overturned and the impurity was placed on its underside.

Generally, we follow the principle that an earthenware container does not contract impurity when a source of impurity is found on its outer surface. This instance is, however, an exception, because the impurity pierces through the pot and is thus found below it as well (Kessef Mishneh).
The Ra’avad emphasizes that in these latter two instances, the impurity does not descend until the very depths of the earth, because it is inside or on top of a container. Instead, the intent is that since the container can contract impurity, it does not intervene in the face of ritual impurity and the impurity passes through to anything above or below it.

Because the impurity ascends upward through the aperture and does not spread throughout the house.

This is referring to a situation where the pot is positioned upright.

Moreover, since there is no open space between the pot and the sides of the aperture, the house and the pot are considered as one structure and the impurity spreads throughout the house (Kessef Mishneh).

This law applies also in a situation where the pot is overturned and the impurity is below it.

Were it able to become impure from its outer surface, it would not be considered as an ohel at all (Kessef Mishneh).

I.e., it is under the aperture leading to the open skies.

Because the object is directly under the open skies.

Because the impurity is directly opposite the aperture and departs through it without being diffused through the house. The area under the pot is pure, because the pot serves as an ohel and prevents the impurity from reaching it [the Rambam’s Commentary to the Mishnah (Ohalot 10:6)].
The Ra’avad and the Kessef Mishneh find the Rambam’s rulings difficult to reconcile with Ohalot 10:6 and also conceptually difficult to understand. The Ra’avad follows a different version of that mishnah which states: “everything is impure.” He explains this version as follows: Since the pot is capable of contracting impurity the impurity pierces through it and makes the space below it impure. The pot then becomes an ohel over that impurity and then joins together with the house to create one single ohel. Diagram

Because there is at least a handbreadth by a handbreadth of open space through which the impurity can ascend.

In his Commentary to the Mishnah (Ohalot 10:7), the Rambam states that this refers to a step at the entrance to the house that is part of the entrance way.

This addition is made on the basis of Rav Kapach’s version of the Rambam’s Commentary to the Mishnah (op. cit). The Ra’avad interprets the mishnah differently and most other commentaries understand the mishnah as he does.

This is speaking about a situation where the pot is partially under the lintel of the house and partially outside it. Regardless of where the impurity is located vis-a-vis the pot, the same laws apply (ibid.), provided the impurity is not under the lintel (Kessef Mishneh).

And does not effect the status of the house at all.

I.e., it is as if the boundaries of the house were extended to include the area under the pot. These diagrams are based on diagrams accompanying the Rambam’s Commentary to the Mishnah (Ohalot 12:5). Diagram

As long as it is less than a handbreadth under the lintel, it is considered as outside the house and is viewed as a separate entity.

Or more.

Our translation is based on the Rambam’s Commentary to the Mishnah (Ohalot 12:5). The Ra’avad objects, stating that it is not necessary for there to be a handbreadth of empty space between the boards. As long as there is some empty space, the impurity does not pass from one board to the other. The Kessef Mishneh maintains that the term “empty space” refers to the height of the empty space between the boards. It is necessary to clarify that there is at least a handbreadth between the upper board and the lower board. Otherwise, any impurity placed on the lower board would be considered as “flush” and would “pierce through and ascend, pierce through and descend.”
Kin’at Eliyahu explains that while the points brought out by the Ra’avad and the Kessef Mishnah are true, the Rambam’s words should be understood as above, for in that way, a parallel can be established with the latter clauses.

Either on the lower beam, below the upper beam, or on the ground, below the lower beam.

For the beam serves as an ohel.

For the upper beam serves as an ohel.

I.e., if an object is positioned over the impurity, it becomes impure.

We follow the principles (Shabbat 101a, Eruvin 4b): gud achit mechitza and gud asik mechitza. Hence, it is considered as if the boards are lowered and/or raised and are all on the same level and thus form one ohel [the Rambam's Commentary to the Mishnah (loc. cit.)].

The Ra’avad emphasizes that this law applies even when the impurity is on the lower beam.

Since there is not a board that is a handbreadth wide, there is no ohel. Even though the boards could be considered as an entire roof based on the principles mentioned in the previous note, since the boards are not a handbreadth wide, we do not follow those principles (see Ra’avad and Kessef Mishneh). See a parallel law regarding the s’chach of a sukkah, Hilchot Sukkah 5:21.

In his Commentary to the Mishnah (Ohalot 11:1), the Rambam states that this is referring to an instance where the split runs over entire roof and walls, dividing the building into two halves.

For the split separates the two portions of the building from each other and the impurity does not spread from one portion to the other.

As the Rambam explains in his Commentary to the Mishnah (loc. cit.), it is the nature of impurity to depart and not to enter. Therefore greater stringency is shown than in the previous clause.

Since the entire building was split, a larger separation was not required (ibid., according to Rav Kappach’s translation).
The Ra’avad does not accept the Rambam’s ruling, based on a different understanding of the above mishnah. The Kessef Mishneh notes that the Rambam’s interpretation is accepted by many other commentaries.

A structure like a patio with a roof, common in Greek and Roman times, built off a wall. In this instance, there is no wall on the far side (Kessef Mishneh).

In his Commentary to the Mishnah (Ohalot 11:3), the Rambam speaks of a crack running across its entire width, breaking the exedra into two, one on the right and one on the left.

The covering on the top joins the two portions of the exedra together as one continuous ohel. Hence, instead of being considered as two separate structures, it is considered as one entity and the impurity from one side spreads to the other.

Only when the k’li was a handbreadth high would it create an ohel that would join the two halves of the exedra into a single structure.

I.e., his inner cavity is not one solid mass.

I.e., we consider it as if the space under the upper garment was empty.