Rambam - 1 Chapter a Day

See Chapter 2, Halachah 1, for more explanation regarding these three sources of impurity.

See ibid.:3-4 regarding these two sources of impurity.

These four sources of impurity are discussed in ibid.:8.

See ibid.:9.

Ibid.:12.

Ibid.:13.

Ibid.:3.

Ibid.:4.

See ibid.:8 regarding these two sources of impurity.

See ibid.:9.

See ibid.:16 regarding these two sources of impurity.

These two terms are defined in ibid.:15.

See ibid.:11.

This phrase indicates a conclusion which the Rambam arrived at through his own process of deduction without an explicit prior Rabbinic source.

As stated in Numbers 6:9-12 and explained in Hilchot Nezirut 6:3,11, if a nazirite incurs impurity through contact with a human corpse, the observance of his nazirite vow is invalidated. He must shave his hair, bring certain sacrifices, and begin counting his nazirite vow anew.

As stated in ibid. 7:6, there are twelve situations which would ordinarily render a person impure, but do not obligate a nazirite to shave his hair because of them. Why should he not shave? Because as long as his nazirite vow is in effect, he is forbidden to shave his hair according to Scriptual Law. Thus shaving to observe a Rabbinic decree concerning impurity would lead to the violation of a Scriptural commandment.
The fact that shaving is not required in the three situations mentioned in this halachah indicates that the impurity is Rabbinic in origin. Why else would they not be required to shave?

See Hilchot Bi’at HaMikdash 3:13-14.

As stated in ibid.:12, “When an impure person willfully enters the Temple, he is punishable by karet, as [Leviticus 17:16] states: ‘If he will not clean [his garments] or wash his flesh, he will bear his iniquity.”‘

The Ra’avad differs with the Rambam on this matter. He states that a limb that does not have a sufficient amount of flesh on it is considered as a bone and, as stated above, a bone the size of a barley-com imparts ritual impurity when touched. Indeed, this is explicitly stated. Similarly, the fact that a revi’it of blood imparts impurity when one is under the same shelter is derived from a verse.
The Kessef Mishneh justifies the Rambam’s approach, explaining that perhaps the limb without flesh is referring to a limb of a fetus that is smaller than a barley-com. Similarly, the verse interpreted to mean that blood imparts impurity when under the same shelter can be understood as an asmachta, i.e., the law is Rabbinic in origin, but the Sages found a verse which could be used as an allusion to it. Although the Rambam himself cites verses as support for these concepts in his Commentary to the Mishnah, these can also be interpreted as asmachtaot. See also Chapter 5, Halachah 5, and notes which refers to the Kessef Mishneh who states that (as the Rambam states in Sefer HaMitzvot, General Principle 2) any concept that is not explicitly stated in the Torah, even through it is derived through accepted techniques of Biblical exegesis, is considered as midivrei sofrim, “from the words of the Sages,” and not from the Torah. See also Chapter 19, Halachah 6.

I.e., substances that will not decompose or rot. In his Commentary to the Mishnah (Ohalot 2:2), the Rambam writes that the coffin cover must also be of such a material.

And Jewish custom is to bury the dead in a shroud.

Before the corpse decomposes entirely, the addition of another substance prevents it from being placed into the category of rekev. Once it is placed in that category, however, the addition of another substance does not remove its impurity (Nidah 27a).

In Hilchot Nizirut 7:3, the Rambam explains the rationale for this ruling. As stated here, for the laws of rekev to apply, the corpse must be entirely intact. When a person was slain, his blood is lacking.

The rationale behind the first and the third clauses is the same: the laws of rekev apply with regard to one body and not two bodies. Even the fetus is considered as a separate entity.
With regard to the second clause, the rationale is that once the hair and/or nails are cut off, they are considered as separate entities. Thus the rekev would not be considered as coming from the body alone.

See Chapter 2, Halachah 11, and notes, for a definition of this concept.

These and the above laws are discussed in Nazir 51a and also stated in Hilchot Nizirut 7:4.

As stated in Chapter 2, Halachah 11, this is the minimum amount required for rekev to impart ritual impurity.

The Kessef Mishneh emphasizes that all the conditions mentioned in Halachah 4 must be met for the rekev to impart ritual impurity.

The liquids produced by a decomposing corpse (Chapter 2, Halachah 1). It is necessary that there be an olive-sized portion of netzal for it to impart impurity.
I.e., the question is whether the substance is primarily the decomposed mass of the corpse with a little earth mixed in or primarily earth with some of the fluids produced when a corpse decomposes.

It does not, however, impart impurity when touched, as stated previously in Chapter 2, Halachah 11.

The Kessef Mishneh questions the Rambam’s wording, because initially, he implies that there is a question about the makeup of this substance: Is it primarily rekev? Or is it primarily earth? And ultimately, he states definitively that it is primarily rekev. The Kessef Mishneh explains that since we are speaking about a corpse that was buried in a stone coffin without anything else being there, we can assume that the mass is primarily rekev.
Although this is not apparent in the Rambam’s words, the simple explanation appears to be that since it is possible that the mixture was primarily rekev, because of the doubt that possibility raises, we rule stringently.

The commentaries point to a similar ruling in Hilchot Shaar Avot HaTum’ah 4:12 where the Rambam writes that he thinks that this impurity is Rabbinic in origin.

In which case it would impart impurity when intact.

For it has lost its natural form. See the Rambam’s Commentary to the Mishnah (Nidah 7:1) which states that even if flesh becomes dry like bone, it imparts ritual impurity. In this instance, however, it is no longer intact and hence, is considered pure.
The Kessef Mishneh notes that this ruling is the subject of a difference of opinion between Rabbi Yochanan and Reish Lakish in Nidah 55a, and the Rambam’s wording appears to follow the opinion of Reish Lakish. This presents a difficulty, because generally, when there is a difference of opinion between these two Sages, the halachah follows Rabbi Yochanan. The Kessef Mishneh explains that the Rambam’s words can be interpreted as meaning, not that the skin has actually become flaky like powder, but that it is so dry that it could become that flaky. Rav Kapach (in his gloss to the Rambam’s Commentary on the Mishnah) suggests that the Rambam had a different version of that Talmudic passage.

The Rambam is following the conception, accepted at the time of the Talmud, that there are worms that are not produced by ordinary reproduction, but rather come into being through spontaneous generation from decomposing matter. See his Commentary to the Mishnah (Ohalot 2:2).

Chapter 2, Halachah 5.

Which also impart ritual impurity. See Hilchot Sha’ar Avat HaTum’ah 1:4, 4:4.

In his Commentary to the Mishnah (Chulin 9:2), the Rambam defines this as the amount of time it would take a person to walk four mil. A mil is equivalent to a kilometer. In his Commentary to the Mishnah (Pesachim 3:2), the Rambam defines that period as 24 minutes. Others give a figure of 18 minutes.

Chulin 122a states: “This is a decree, lest a person make carpets out of the skin of his father and mother.”

This refers to the placenta which is not considered as part of the body of either the mother or the child.

Note the parallel in Hilchot Ma’achalat Assurat 4:20.

And can impart that impurity.

I.e., when separated from the corpse.

I.e., they are not permanent parts of a person’s body, as indicated by the fact that they are removed and others grow in their place. Niddah 55a, the source for the Rambam’s statements, notes that some teeth are not replaced. Nevertheless, they are not considered as permanent parts of the body because they did not exist when the person was born. The Rambam does not elaborate, because there is no halachic difference involved (Kessef Mishneh).

Because of the impurity contracted through ahel, being under the same shelter.

See Hilchot Mechirah 1:17, Hilchot To’en v’Nit’an 5:4, which state that produce which is ready to be picked is considered as if it has been picked even though it remains attached. On the other hand, from Hilchot Me’ilah 5:10, one could conclude otherwise. Since there is no clear-cut ruling concerning the matter, the Rambam leaves the issue undecided.

Chapter 2, Halachah 12.

See Hilchot Shaar Avot HaTum’ah 10:4.

See Rashi, Chulin 109b, who states that “a liver is entirely blood.”