1)

(a)One of the two practical differences between the Zov of a Zav and the Keri of a Ba'al-Keri is that the former comes from an Eiver Meis (a limp limb), the latter, from an Eiver Chai (one that is stiff). The other is that - the former is like the white of an egg that is liquid, the latter, like the white of an egg that is viscuous.

(b)When Beis Shamai say that the first sighting of a Zav has the Din of Shomeres Yom Keneged Yom of a Zavah, they mean that - he is Metamei Mishkav and Moshav (see Tos. Yom-Tov).

(c)Beis Hillel consider him - like a Ba'al-Keri ...

(d)... which renders a Rishon whatever it touches (be'Maga, but not be'Masa and certainly not be'Mishkav and be'Moshav).

2)

(a)We learn from the fact that one Pasuk in Tazri'a writes "Zav mi'Besaro Zovo, Tamei hu", and another Pasuk there writes "ve'Zos Tih'yeh Tum'aso be'Zovo Rar Besaro es Zovo O Hechtim Besaro mi'Zovo, Tamei hu" - there are two levels of Zav; one who has had two sightings, and one who has had three ...

(b)... at which point he becomes Chayav to bring a Korban (which one who had two sightings is not).

(c)The Din of a Zavah is different in this regard in that - if she has three sightings ...

1. ... in one day or ...

2. ... in two days - she is a Shomeres Yom Keneged Yom.

3. ... in three days - she becomes a Zavah.

(d)Based on the above Pasuk and the Pasuk written in connection with a Zavah "ve'Ishah ki Sazuv Zov Damah Yamim Rabim be'Lo Es Nidasah", the basic difference between a Zav and a Zavah is that - the Zivus of a Zav depends on sightings, whereas that of a Zavah depends on days.

3)

(a)According to the Tana Kama, Beis Shamai rule that a man who has one sighting on Sunday, none on Monday and on Tuesday ...

1. ... two or ...

2. ... one sighting which lasted as long as two (see Tiferes Yisrael) - is a full Zav.

(b)According to Beis Hillel - he is Metamei Mishkav and Moshav like a Zav who has had two sightings (see Tos. Yom-Tov) ...

(c)... because the day on which he did not have a sighting negated his earlier one.

(d)The latter, according to Beis Hillel, is obligated to Tovel - in Mayim Chayim (spring water).

(e)The other ramifications of this Machlokes are that - according to Beis Shamai, he is obligated to bring a Korban, whereas according to Beis Hillel, he is not.

4)

(a)R. Eliezer ben Yehudah disagrees with the Tana Kama - inasmuch as, according to him, Beis Shamai will concede to Beis Hillel that if the two sightings occur on the third day, he only has the Din of a Shomeres Yom Keneged Yom.

(b)And he presents the Machlokes in a case - where the Zav had two sightings on the first day, none on the second, and one, on the third.

(c)Beis Shamai's reason is - because, since she already became obligated to count seven days with her first double-sighting, her third sighting negates the Tahor day in between.

5)

(a)According to Beis Shamai, if a Zav who had two sightings sees Keri on the third day of the seven clean days, he must start counting from scratch. Beis Hillel maintain - that he only needs to repeat the third day.

(b)In the same case but where he saw Keri on the second day, R. Yishmael holds that - Beis Hillel concede to Beis Shamai that he must begin the seven days from scratch.

(c)According to R. Akiva - Beis Hillel retain their initial ruling (that he only needs to repeat the second day [see Tos. Yom-Tov]).

6)

(a)If the Zav sees Keri on the fourth day - even Beis Shamai will agree that he only needs to repeat that day ...

(b)... since he had three clean days, like the three days that made him a Zav.

(c)The source for the Din that Keri interrupts the clean days is - the Pasuk "Zos Toras ha'Zav va'asher Teitzei mimenu Shichvas-Zara" (comparing Zera to Zivus in this regard).

(d)We learn from the Pasuk "le'Tam'ah bah" that - it only negates one day (and not the entire seven, like Zivus does, as we will now see).

7)

(a)Should the Zav see Zivus on the fourth day (and even on the seventh) - then even Beis Shamai will agree that he must start counting the seven clean days all over again ...

(b)... because the Torah writes "Shiv'as Yamim le'Taharaso", implying that a Zav requires seven consecutive clean days.

8)

(a)A man who has ...

1. ... one sighting of Zivus on one day and two on the next, or vice-versa ...

2. ... three sightings on three consecutive days, or ...

3. ... three sightings on three consecutive nights - is a full Zav.

(b)We learn from the Pasuk "Tum'aso be'Zovo" - that (unlike a Zavah), the status of Zav is determined by sightings and not by days (as we explained earlier).

(c)If the man does not see for one day ...

1. ... in between two sightings of Zivus - he is not a Zav at all.

2. ... in the middle of three days of Zivus - he is Patur from a Korban.

9)

(a)One sighting that extends for the length of two - is considered two sightings.

(b)To be considered two sightings - the sighting must last the amount of time it takes to Tovel and dry oneself (see Tos. Yom-Tov) ...

(c)... and the same time-period is required for a Hefsek (a break during a sighting) to turn one sighting into two.

(d)The Tana rules that a man who has ...

1. ... three sightings on one day ...

2. ... one extended sighting followed by a third one, or vice-versa, all on the same day - is a full Zav.

10)

(a)The Mishnah declares a man who has one sighting that lasts as long as three - a full Zav.

(b)The Tana describes this as 'ke'Miyn Gad Yavan la'Shilo'ach'. Shilo'ach refers to the spring of water outside Yerushalayim; ke'Miyn Gad Yavan refers to - a location where the Greeks placed an image by the name of Gad.

(c)What the Mishnah now means is - the time it takes to walk from the Shilo'ach to that specific location ...

(d)... which, in practical terms, is equivalent to two Tevilos and two dryings (see Tos. Yom-Tov).

11)

(a)The Tana Kama rules that a man has either two sightings of Zivus or one sighting that extends for the period of two ...

1. ... is Metamsi Mishkav and Moshav and requires Tevilah in spring-water ...

2. ... but is not obligated to bring a Korban.

(b)R. Yossi declares a man who has one sighting that extends for the period of ...

1. ... two - Tahor.

2. ... three - Tamei (see Tos. Yom-Tov).

12)

(a)The Mishnah now discusses sightings during Bein-ha'Shemashos (dusk). Someone who has one sighting in the day and one extended sighting during Bein-ha'Shemashos, or one during Bein-ha'Shemashos and one in the night is ...

1. ... a full Zav (see Tos. Yom-Tov) - provided he knows that he saw part of the Bein-ha'Shemashos sighting during the day and part, during the night

2. ... Vaday le'Tum'ah ve'Safek le'Korban - if the entire sighting may have taken either during the day or during the night.

(b)One can know for sure that part of the sighting took place in the day, and part in the night - if it began before Bein-ha'Shemashos and ended after Bein-ha'Shemashos.

(c)The fact that it lasts for the entire duration of Beis-Hashemashos will not suffice to render it two sightings - because although it is possible that Bein-ha'Shemashos is half-day, half-night, it is also possible that the entire period belongs either to the day or to the night.

13)

(a)The Tana rules that someone who has two sightings on two consecutive Bein-ha'Shemashos - is a. Safek Tamei, b. Safek Chayav Korban (incorporating three possibilities, Safek Tahor, Safek Tamei [requiring seven clean days], Safek Chayav Korban).

(b)He will be ...

1. ... Tahor - if the first sighting took place at the beginning of the first Bein-ha'Shemashos, and the second one, at the end of the second (see Tos. Yom-Tov), assuming that the first half of Bein-ha'Shemashos belongs to the day, and the second half, to the night.

2. ... Tamei but Patur from a Korban - if we assume that Bein-ha'Shemashos belongs either to the day or to the night.

3. ... Tamei and Chayav a Korban - if we assume that either the beginning or the end of Bein-ha'Shemashos belongs both to the day and to the night (see Tos. Yom-Tov).

(c)He must therefore - observe seven clean days, and bring a Korban, which is not eaten.

(d)And the Mishnah finally rules that somebody who has one sighting on one Bein-ha'Shemashos is - Safek Tamei (Zav) ...

(e)... since maybe he only had one sighting.