Rambam - 1 Chapter a Day

One who is impure — even if he is impure because of another type of impurity and not because of contact with a corpse- cannot perform this sprinkling, because Numbers 19:19 specifically mentions that it must be performed by one who is pure. See the notes to Chapter 15, Halachah 1, which state that this purification process is considered an element of one of the 613 mitzvot.

A semi-woody plant, native from the Mediterranean east to central Asia. It is aromatic, with erect, branched stems up to 60 cm long covered with fine hairs at the tips. It is also employed in the purification process of a person afflicted with a tzara’at blemish (Hilchot Tum’at Tzara’at 11:1).

In his Commentary to the Mishnah (Parah 11 :9), the Rambam explains that this concept is derived from the fact that with regard to the offering of the Paschal sacrifice in Egypt, Exodus 12:22 speaks of taking a bundle of hyssop. The Kessef Mishneh states that binding the hyssop is the optimum way of fulfilling the mitzvah, but, after the fact, the sprinkling is acceptable even if the hyssop was not bound.

See Chapter 10, Halachah 7.

As stated in Numbers 19:19. See the following halachah which explains that sprinkling the water with the ashes on the third and seventh days is the earliest possible options, but that one may delay the sprinkling if he so desires or has no opportunity to do it earlier.

Numbers, op. cit. mentions sprinkling on the third and seventh days. From this, Megilah 20a derives the ruling that one may sprinkle the water only during the day.

The appearance of the first glimmerings of the light of the sun on the horizon more than an hour before sunrise.

Here as well, as stated in the following halachah, one may immerse afterwards. This, however, represents the earliest opportunity one has to purify himself.

As indicated by Chapter 15, Halachah 1, the water from an invalid sprinkling imparts impurity.

A common person is not aware of the details of the laws of ritual purity and may contract impurity without knowing it.

One who is both knowledgeable of the laws of ritual impurity and meticulous in their observance. See Hilchot Metamei Mishkav UMoshav, ch. 11, for a detailed definition of this term.

In his Commentary to the Mishnah (Parah 12:12), the Rambam emphasizes that although the Torah mentions sprinkling the water on the third and seventh days, that is not an absolute requirement. Moreover, even though there are more than four days between one sprinkling and the next, the second sprinkling is acceptable.

This applies only when the sprinkling is delayed. When one sprinkles on the seventh day, the sprinkling must precede the immersion.

I.e., the night between the eighth day and the ninth day.

He need not immerse himself again after the sprinkling.
The Ra’avad differs with the Rambam on both these points, requiring a four day interval between the first and the second sprinkling (see Kiddushin 62a) and requiring that the sprinkling precede the immersion. The Kessef Mishneh states that the Rambam’s ruling is based on the Sifri and other Midrashic sources. He also suggests that the Rambam had a slightly different version on Kiddushin, for, otherwise, it is not logical to assume that he would favor a ruling of the Midrash over one from the Talmud.
The Kessel Mishneh also cites the view of Rabbenu Tam who requires two immersions on the seventh day: one in preparation for the sprinkling and one, afterwards. The Rambam, however, does not follow this approach.

The term refers to men who have three successive emissions from their sexual organs similar to those resulting from a gonorrheal infection. Such individuals are ritually impure as stated in Leviticus, ch. 15; Hilchot Mechusrei Kaparah 2:1; Hilchot Metamei Mishkav UMoshav, ch. 1.

Women who experience vaginal bleeding for three consecutive days outside their menstrual cycle. Their impurity is mentioned in Leviticus, op. cit.; Hilchot Mechusrei Kaparah 1:6; Hilchot Metamei Mishkav UMoshav, ch. 1.

Their impurity is mentioned in Leviticus, op. cit.; Hilchot Issurei Bi’ah, ch. 4; Hilchot Metamei Mishkav UMoshav, ch.1.

Their impurity is mentioned in Leviticus, ch. 12; Hilchot Issurei Bi’ah, ch. 10; Hilchot Metamei Mishkav UMoshav, ch. 1.

Which has certain aspects that are more severe than other forms of impurity.

Yevamot 71b cites the historical precedent of our ancestors in Egypt who circumcised themselves and then partook of the Paschal sacrifice.

It appears, however, that one hyssop stalk is not acceptable (Kessel Mishneh).

Each on a small stalk of its own.

Thus producing three stalks.

I.e., so short that when one holds it in his hand, it will be impossible to dip it into the water.

For one must sprinkle with the hyssop itself. It is not sufficient to sprinkle with it while holding another object to which it is attached.

The rationale is that it is certain that the person was impure and there is a doubt whether a proper sprinkling was performed to bring him to a state of purity. His status does not change until a sprinkling is performed that is known to be valid.

A hyssop carries its seeds in small pouches that grow at the top of the stalks [the Rambam’s Commentary to the Mishnah (Parah 11:7)].

An impure person is liable for entering the Temple. Although having the water sprinkled on oneself with an underdeveloped hyssop is not desirable or permitted, since the water was sprinkled on him, it cannot be said that he defiled the Temple (ibid.).

The fact that it was used for one mitzvah does not prevent it from being used for another.

As the Rambam provides examples at the conclusion of the halachah.

I.e., a person who sees it will call it a hyssop and not add any other descriptive term (ibid.:7).

A plant that is worshiped. See Hilchot Avodat Kochavim 8:3.

A city in which the majority of the inhabitants were led astray to serve idols. In such an instance, all of the city's inhabitants must be killed and all of its property destroyed (ibid. 4:6).

When a hyssop was sown to be eaten, terumah and the tithes must be separated from it [the Rambam’s Commentary to the Mishnah (Parah 11:7)]. If a hyssop was designated as terumah and then became impure, it should not be used for sprinkling. The rationale is that since Numbers 19:19 states: “The pure person shall sprinkle on the impure,” our Sages understood that everything used in the purification process must be pure.
In his Commentary to the Mishnah (op. cit.), the Rambam asks: If the hyssop was designated as food, it will impart its impurity to the water and disqualify it. Why then is a special teaching required for us to derive that it is unacceptable? In resolution, he explains that here we are speaking about hyssop that is lesser than an egg-sized portion in size. In such an instance, it would never impart ritual impurity.

The rationale is that the hyssop must be a minimum length and since these hyssops are consigned to be destroyed by fire, they are not considered to be of that length.
The commentaries note that although an object connected with idolatry must be burnt, that requirement does not apply if a gentile nullifies its connection with idolatry before it comes into a Jew’s possession. For that reason, the Rambam rules (Hilchot Lulav 8:1) that a lulav belonging to a false deity is acceptable after the fact. Among the resolutions offered is that here we are speaking about a false deity belonging to a Jew, in which instance, the above leniency does not apply.

Because one should endeavor to prevent terumah from becoming susceptible to ritual impurity, and, by immersing it in the water, one makes it susceptible (see ibid.:2).

Because there is no difficulty with the hyssop, only with the terumah.

If liquids fell on a hyssop that was reaped for use as food, it becomes susceptible to ritual impurity. Now, because of the stringencies applied with regard to the water for the ashes of the red heifer, once it is even susceptible to impurity, it is considered as if it is actually impure and disqualified for use, as stated in the following halachah. In this instance, however, the hyssop was not reaped with the intent that it be eaten and it is a species that is not always used as a food. Therefore, the fact that it came in contact with liquid does not make it susceptible to ritual impurity (see Hilchot Tum’at Ochalin 1:1).

So the water on it will not become mixed with the water of the ashes of the red heifer.

Even if it did not actually contract impurity, the fact that it became susceptible to impurity is enough to disqualify it, as the Rambam proceeds to explain.

See Chapter 13, Halachah 1.

For it is not being used as food.