(Mishnah): Blood and flesh of a Sheretz join with each other;

R. Yehoshua says, the general rule is -- things join for a Shi'ur of Tum'ah if the same Tum'ah and Shi'ur apply to them;

If they have the same Tum'ah but different Shi'urim, or the same Shi'ur but different Tum'os, they do not join. (We adopt the text in the margin.)

(Gemara - R. Chanin): Only blood and flesh of the same Sheretz join with each other.

Question (R. Yosi b'Rebbi Chanina - Beraisa): (The "Hei" in) "ha'Teme'im" teaches that different Sheratzim join with each other, and that the blood joins with the flesh, whether they are the same or different species (among the eight).

Version #1 (Rashi) Answer (Rav Yosef): If the blood and flesh came from whole Sheratzim, (they are important, so) they join, even if they are from different species;

If they came from partial Sheratzim, they join only if they are from the same Sheretz.

Version #2 (Tosfos) Answer (Rav Yosef): If the blood and flesh came from different Sheratzim, he is not Tamei unless he touched each one;

If they came from the same Sheretz, he is Tamei even if he touched only one (while it was touching the other). (end of Version #2)

Rav Yosef: The following is my source to make such a distinction:

(Beraisa): If a Revi'is of blood (of a Mes) spilled on a (smooth,) inclined floor, and one was Ma'ahil (towered) above some of it, he is Tahor. If he was Ma'ahil above all of it, he is Tamei.

Question: What does "some of it" mean?

Version #1 (Rashi) Suggestion: He was Ma'ahil above some of the blood. (However, if he was Ma'ahil above all of the blood, he is Tamei.)

Rejection: R. Chanina taught that if one stirred a Revi'is of blood, he is Tahor (even though he is Ma'ahil above all of it)!

Answer: Rather, "some of it" means that the blood came from a partial Mes. If it came from a full Mes, one who was Ma'ahil above it is Tamei.

Version #2 (Tosfos) Suggestion: He was Ma'ahil above less than a Revi'is of blood. (However, a full Revi'is is Metamei, even if he was not Ma'ahil above all of it.)

Rejection: R. Chanina taught that if one stirred (even) a (full) Revi'is of blood, he is Tahor (because he was not Ma'ahil over all of it)!

Answer: Rather, "some of it" means, he was Ma'ahil above some of the blood (but if he was Ma'ahil above all of it, he is Tamei). (end of Version #2)

Question (R. Masya ben Charash): What is the source that blood of Sheratzim is Tamei?

Answer (R. Shimon): We learn from "v'Zeh Lachem ha'Tamei."

Talmidim of R. Masya: R. Shimon is a great Chacham!

R. Masya: He did not expound that himself. He heard it from R. Elazar bar R. Yosi.

Once, the Romans decreed that the Yisraelim may not observe Shabbos, circumcision and Nidah. R. Reuven ben Istrobli cut his hair like (and pretended to be) a Nochri, and sat with the legislators.

R. Reuven: Does one want his enemy to become poor, or to become rich?

The legislators: He should become poor!

R. Reuven: If so, we should allow the Yisraelim to cease from working on Shabbos, in order that they will become poor!

The legislators: You are right. (They repealed the decree.)

R. Reuven: Does one want his enemy to become weak, or healthy?

The legislators: He should become weak!

R. Reuven: If so, we should allow the Yisraelim to circumcise, in order that they will become weak!

The legislators: You are right, (they repealed the decree.)

R. Reuven: Does one want his enemies to increase, or decrease?

The legislators: They should decrease!

R. Reuven: If so, we should allow the Yisraelim to refrain from relations with Nidos, in order that they will decrease!

The legislators: You are right. (They repealed the decree.)

Later, the legislators realized that R. Reuven was a Yisrael, and they reinstated the decrees.

The Rabanan sought to send sages to go to Rome to petition for the annulment of the decrees. They chose R. Shimon bar Yochai, for many miracles were done for him (in the cave), and also R. Elazar b'Rebbi Yosi.

R. Yosi: If my father was alive, you could not tell him to endanger his son! (Likewise, how can you tell me to endanger my son and let him go?)

R. Shimon: If my father was alive, you could not tell him to endanger his son! (Nevertheless, I agree to go. Likewise, R. Elazar should go!)

R. Yosi: I will go instead. I fear (not of the journey or kingdom, rather, the wrath of R. Shimon, lest my son teach Halachah in front of him, and) that R. Shimon will punish him! (I do not fear for myself. I am entitled to teach in front of him.)

R. Shimon agreed not to punish R. Elazar. In the end, he (forgot and) punished him. (When he remembered, he prayed that Hash-m cure him, and was answered).

When they were traveling, someone asked "what is the source that blood of Sheratzim is Tamei?" R. Elazar moved his lips and whispered that we learn it from "v'Zeh Lachem ha'Tamei."

R. Shimon: The contortion of your lips shows that you (think that) you are a Chacham (fit to rule in front of me). You should not return to your father! (One who teaches in front of his Rebbi is Chayav Misah b'Yedei Shamayim - Berachos 31b.)

A certain Shed offered to go with them (to help them).

R. Shimon cried. 'Three angels came to the maidservant (Hagar) of my ancestor (we learn from the repetitions of the word "Mal'ach"), while not even one comes for me! (You may come;) we will accept the miracle however it comes. (Maharsha - the Shed had caused the decree, therefore it helped annul it.)

The Shed entered the Kaisar's daughter, and made her insane. No one could cure her, until R. Shimon and R. Elazar came and told the Shed to leave.

They allowed R. Shimon and R. Elazar to take anything from their treasure house. They saw the parchment on which the decree was written. They took it and tore it up.

Regarding this episode R. Elazar taught (in a Beraisa) "I saw (the Paroches) in Rome (who destroyed and pillaged the Mikdash). It had many drops of blood (that the Kohen Gadol sprinkles from the bull and goat on Yom Kipur)."

(Mishnah): Pigul and Nosar do not join, for they are different Shemos (of Isur);

The following Tum'os do not join to be Metamei even like the milder Tum'ah --

Sheretz and Nevelah;

Nevelah and flesh of a Mes.

(Gemara - Rav Yehudah): (Chachamim decreed that Pigul and Nosar are Metamei the hands, in order that Kohanim ensure that they not occur.) They do not join for a Shi'ur for Tum'as Yadayim (for this would be like a decree to guard a decree), but they join regarding eating.

(R. Eliezer): "Lo Yochal Ki Kodesh Hem" is a Lav for eating any Pasul Kodshim. (This shows only that they join to be Mechayev a Lav. Indeed, Tosfos (Kerisus 11b, DH she'Im) says that they join only for a Lav. Rashi and Rambam do not distinguish. Apparently they hold that they join even for Kares and Korban.)

(Mishnah): Food that became Tamei through an Av ha'Tum'ah (the food is a Rishon) joins with food that became Tamei through a Rishon (the latter is a Sheni) to be Metamei like the more lenient one (a Sheni. Together, they make a Shelishi.)

All foods join for the following --

To be Metamei (mid'Rabanan) one who eats a half-loaf (the volume of two (Rashi) or one and a half (Rambam) eggs) of Tamei food;

To the Shi'ur of two meals needed for Eruv (Techumim, to permit going more than 2000 Amos outside the city on Shabbos);

To the Shi'ur of an egg for Tum'as Ochlim (to be Metamei other foods; alternatively, to be Mekabel Tum'ah mid'Oraisa, or for Hechsher, i.e. if liquid is put on it, it becomes able to receive Tum'ah).

To the Shi'ur of a dry fig to be liable (for Melachos involving food) on Shabbos;

To the Shi'ur of a large date to be liable for eating on Yom Kipur;

All beverages join to be Metamei one who drinks a Revi'is of Tamei liquids, and to the Shi'ur of Malei Lugmav (the capacity of the mouth and one cheek) to be liable for drinking on Yom Kipur.

(Gemara - Beraisa - R. Shimon): They join because a Sheni can make (be Metamei something else to be) a Rishon.

Objection: A Sheni cannot make a Rishon!

Answer #1 (Rava): He means that a Sheni became a Sheni through a Rishon.

Answer #2 (Rav Ashi): A Sheni and a Rishon are "housemates" with respect to a Shelishi. (There is no Halachic difference between Rav Ashi and Rava.)