Rambam - 1 Chapter a Day

Even without lifting it up or touching it.

And a zavah, a nidah, and a woman after childbirth, according to Scriptural Law, and a gentile, according to Rabbinic Law.

Which can never regain ritual purity.

1n truth, even if the earthenware container is not sealed close, it and its contents are pure if a zav touches merely its outer surface. The Rambam speaks about a container that is sealed close to emphasize the contrast. Even the impurity associated with a human corpse, the most severe form of impurity that exists, does not change the status of a sealed container and yet, its status is changed when it is moved by a zav.

See Hilchot Tuma’at Meit 6:3, 21:1, which mention how such a seal preserves the purity of the contents of a container when it is located in a tent in which a human corpse is found. The rationale is that an earthenware container contracts impurity only from its inner space and, in this instance, the inner space is sealed shut [the Rambam's Commentary to the Mishnah (Eduyot 2:5)].

In his Commentary to the Mishnah (op. cit.), the Rambam explains that an empty clay ball would be made and inserted into a kiln to be fired. Afterwards, it would be taken out and cut into half to produce two frying pans. The halachah is speaking about an instance where it was touched by a zav before it was cut in half.

See Hilchot Tum’at Meit 20:5 which states that being embedded in such a manner does not prevent an article from contracting impurity when it is located within the inner space of an earthenware container.

Although the Rambam began the halachah speaking about a zav, here he mentions a nidah, because he is borrowing our Sages’ wording (Shabbat 82b). 1n practice, the same laws apply both to a zav and to a nidah.

I.e., when a zav inserts a limb into the inner space of a container, he does not impart impurity. It is only his entire body that imparts impurity. Compare to Hilchot Tum'at Meit 6:3, where the Rambam rules that the limb of a corpse imparts impurity in such a manner, and Hilchot Sha'ar Avot HaTum'ah 6:3, where he rules that a false deity only imparts impurity when intact.

The folds of the skin are not considered as open and revealed parts of the body, but instead, as a hidden part of the body, like one’s throat. Hence, unlike one’s other limbs, they do not impart impurity through moving an object, as the Rambam proceeds to explain.

For there is no way that a person can touch another entity with the hidden portions of his body on his own initiative alone.

I.e., they become derivatives of impurity, not primary sources of impurity.

In his Commentary to the Mishnah (Zavim 4:6), the Rambam states that in either case, it is considered that they were moved by the zav which is equivalent to being touched by him.

The same laws also apply if pure keilim, foods, or liquids were placed on the opposite side of the zav.

I.e., the board or the bench was not firmly affixed in place and moved up and down depending on the shifting of the weight of the persons sitting. The Ram bam conveys this in a picturesque manner, saying that they are "limping," i.e., just as a person with a limp shifts his body weight as he walks, so too, the position of these individuals is shifting.

And thus the movement of one would shake the trunk and move the other.

A kab is comprised of four luggim. A revi’it (fourth) of a log is a commonly used Talmudic measure, comprising 86 cc according to Shiurei Torah and 150 cc according to Chazon Ish. Thus a fourth of a kab would be 344 cc or 600 cc depending on these opinions.

A small ladder; any person who climbs on it will cause it to move.

For the movement of the zav will have no effect on the pure person.

Since they are pulling in the same direction and relatively little effort is invested, one person's acts do not affect the other.

Since the two are pulling in opposite directions, the position of one will inevitably be shifted by the other.

Pulling him up with a rope without touching him by hand.

Even if a small portion of the body of the pure person (or the zav) is moved by pulling the rope, the pure person contracts impurity.

For inevitably, the movement of one will affect the other.

R. Yosef Corcus maintains that the intent is that he does not contract the severe impurity of midras which would cause him to became a primary source of impurity. He personally is impure. Although this interpretation is given by others to the Rambam's source, Zavim 3:3, it is, however, difficult to reconcile with the Rambam's wording.

I.e., becomes a primary source of impurity, as the Rambam proceeds to explain.

And serving as a support. Hence, he becomes a primary source of impurity, as explained in ch. 7.

In Chapter 7, Halachah 3, it was emphasized that in order to become a primary source of impurity, the majority of a person's body had to be supported. Here the Rambam is pointing out that for the pure person to contract impurity himself, it is sufficient that even a minor portion of his body be involved.

And thus one has not touched the other.

This expression indicates that the ruling to be mentioned has no explicit source in the prior Rabbinic literature.