Rambam - 1 Chapter a Day

If it is touched by impurity from the outside, it remains pure.

The Rambam uses the expression kal vichomer, a conclusion drawn from a more stringent situation to a more lenient one (a fortiori reasoning). The logic is that if the sealed covering can protect the contents of a container that is susceptible to ritual impurity, it certainly will protect the contents of a container that is not susceptible to ritual impurity.

See Chapter 6, Halachot 1-3, for an explanation of this concept.

See the notes to the above source where a distinction is made between earthenware keilim and keilim that are made from earth.

The same leniency applies also to sea animals that are not fish per se. See Hilchot Keilim 1:3.

I.e., that a wooden board should be placed on top of a container and then fastened close [the Rambam's Commentary to the Mishnah (Keilim 10:1)].

See Hilchot Keilim 8:1-5 for an explanation of this point.

Here also, the Rambam uses the expression kal vichomer. The logic is that if the sealed covering can protect the contents of a container from impurity, certainly, the fact that a k’li is swallowed or separated by an ohel will protect it.

The Ra’avad objects to the Rambam’s ruling, maintaining that the hole must be closed for the funnel to be considered as a covering. The Kessef Mishneh differs and maintains that even if it is open, since this is the way such a utensil is made, it is considered as a valid covering.

I.e., even articles buried in the earth.

To seal it to the ground, as it were.

I.e., over its opening.

For then it is considered as sealed close.

In the previous clause.

For an ohel must be a handbreadth by a handbreadth by a handbreadth (Kessef Mishneh).

Either the border of the wall or the utensil.

Thus the inner space of the container is considered as covered by the tent.

Thus the beam is serving as an ohel over the impurity.

If even a portion of the pot was uncovered, its contents are impure. For it to be saved from impurity, it must be covered entirely.

Even the smallest amount of empty space enables the impurity to enter. See the Rambam’s Commentary to the Mishnah (Ohalot 5:7).

For the space under the beam is impure and that impurity enters the pot.

In this and the next halachah, we translate both the Hebrew terms bor and chadut as “cistern.” In particular, however, there is a distinction between them. As the Rambam writes in his Commentary to the Mishnah (Ohalot 5:6, et al), a bor is a pit dug in the ground. A chadut is a storage area that is built above the ground.

A flat board is not considered as a k’li. Therefore it is not susceptible to ritual impurity and hence can serve as a covering that protects the contents of the cistern.
The Ra’avad differs with the Rambam, noting that from the mishnah in Ohalot, it appears that even a flat utensil can also serve as a covering to the cistern. The Kessef Mishneh suggests that the Rambam would not contest that statement and considers a flat utensil as similar to a board.

See Halachah 3 which explains that such a utensil serves as an ohel.

In his Commentary to the Mishnah (loc. cit.), the Rambam emphasizes that this applies only when the k’li is not susceptible to ritual impurity,

In his Commentary to the Mishnah (Keilim 11:7; Ohalot 11:8) the Rambam defines this term as referring to the round plate of a lamp on which the actual candle or wick is placed.

I.e., the flower of the lamp protrudes above the cistern and the utensil rests on it.

Obviously, if its support would be removed, it would descend. The question is whether it will fall into the cistern or not? I.e., is it large enough to serve as a covering for the cistern?

For the cover serves as an ohel and protects everything under it.

Since the cover is supported by the flower and the flower is susceptible to ritual impurity in this instance, the cover is considered like the flower and is not considered to have formed an ohel.

Here also we are speaking about a cistern built inside a house, where the walls of the cistern project above the ground.

Chapter 20, Halachah 1.

I.e., the minimum size of an ohel.

This ·refers to a situation where storage areas are hollowed out in the walls of the cistern. They are not considered as part of the house, but as part of the cistern. Just as the cistern protects the keilim in it, it protects the keilim in its walls [the Rambam's Commentary to the Mishnah (Ohalot 11:9)].

For then, they are considered as part of the house.

I.e., the cistern was built under the wall of the house, half opens up inside the house and half opens up outside.

I.e., even if it does not have a cubic handbreadth of empty space. Since the walls of the cistern extend beyond the walls of the house, the entities in its walls are never considered as part of the house.

Chapter 12, Halachah 3.

This refers to an oven that had not been used yet.

In his Commentary to the Mishnah (Keilim 9:7), the Rambam explains that this refers to a flat earthenware surface with holes in it.

I.e., the old oven projects somewhat outside the new oven. Although the covering is resting primarily on the new oven, it is supported somewhat by the old one.

In contrast to the new oven, the old oven is considered as a k’li and a cover must be fastened on to it for it to protect from ritual impurity [the Rambam’s Commentary to the Mishnah (Keilim 10:7)].

I.e., in the new oven and of course, in the old oven.

For the cover is considered as an ohel on top of the new oven which is also an ohel. Hence it protects the keilim from impurity.

And thus the covering is considered as an ohel.

Since there is less than a handbreadth of open space there, the impurity does not enter and thus the oven is considered as covered even if it is not sealed close. [It must be noted that Rav Kappach’s edition of the Rambam’s Commentary to the Mishnah (Keilim 10:7) includes an emendation of the version of the Rambm’s commentary that differs from the version that appears in the standard published texts. The version in Rav Kappach’s text fits the ruling here.]

Since the covering has a border, it is considered as a k’li and like other keilim, it does not intervene in the face of ritual impurity, as a flat covering would.

Even the slightest amount [the Rambam’s Commentary to the Mishnah (Ohalot 12:2)]. In that source, the Rambam also quotes the Tosefta (Ohalot 13:5) which explains that we are speaking about a covering with a border.

Since the oven is sealed close, it makes no difference whether it is new or old.

The commentaries question the addition of the term “even.”

I.e., above or under the portion that projects beyond the oven.

I.e., if the impurity is below the covering, the covering serves as an ohel and imparts impurity to the entire space and any keilim under it. Nevertheless, the covering does not intervene in the face of impurity. Hence, the impurity rises through the covering and imparts impurity to everything above it. If the impurity is above the covering, the covering does not intervene and the impurity descends through it. The covering then serves as an ohel and imparts impurity to the entire space and any keilim under it. That impurity then rises through the covering and imparts impurity to everything above it [the gloss of Rav Ovadiah of Bartenura (Taharot 12:2)].

Because the oven is closed with a sealed covering.

Because it is covered by a sealed covering.

Because it is considered as a sealed covering.

Which, in contrast to the first clause, is, in this instance, open to contract the impurity in the house.

I.e., the pot cannot serve as a covering for the jug.

Chapter 13, Halachah 4.