Question: The Tana holds that one who eats a Rishon or Sheni is Posel Terumah, he does not Metamei it (make it able to Posel other Terumah, e.g. a Sheni) - who is the Tana?

Answer (Rabah bar bar Chanah): It is R. Yehoshua:

(Mishnah - R. Eliezer): One who eats a Rishon becomes a Rishon, one who eats a Sheni becomes a Sheni, one who eats a Shelishi becomes a Shelishi;

R. Yehoshua says, one who eats a Rishon or Sheni becomes a Sheni; Sheni becomes a Sheni, one who eats a Shelishi becomes a Sheni regarding Kodesh, but not regarding Terumah;

This refers to Chulin Al Taharas (guarded as if they were) Terumah (but regular Chulin cannot become a Shelishi).

Question: Why did they decree that one who eats a Rishon or Sheni becomes a Sheni?

Answer: This is a decree lest he put Terumah liquids in his mouth together with Tamei food, which would Posel the Terumah.

Question: Why did they decree that one who drinks a Tamei liquid becomes a Sheni?

Answer: This is a decree lest he put Terumah food in his mouth together with Tamei liquids.

Question: This is just like the previous decree (why are they counted separately)?

Answer: One might have thought that we do not make the latter decree, because [it is common to drink while eating, but] it is not common to eat while drinking - the Mishnah teaches, this is not so.

(Mishnah): One [a Tevul Yom] who entered his head or his majority in Mayim She'uvim [is Posel Terumah].

Question: Why was this decreed?

Answer: People used to immerse in [Mikva'os of] stinking water in caves; afterwards, they would pour [three Lugim of] Mayim She'uvim on their heads - it became Keva (primary), so they decreed about it.

Question: What does it mean, 'it became Keva'?

Answer #1 (Abaye): People used to say that the Mikvah is not Metaher without the Mayim She'uvim.

Objection (Rava): That would not be a problem, for they would continue to immerse in the Mikvah!

Answer #2 (Rava): People used to say that the Mikvah is not Metaher, only the Mayim She'uvim are.

(Mishnah): A Tahor who had three Lugim of Mayim She'uvim poured on his head.

Question: Why was this decreed (the above reason applies only to a Tevul Yom)?!

Answer: If not for this decree on all people, the decree on a Tevul Yom would not be followed.

(Mishnah): One who touched a Sefer.

Question: Why was this decreed?

Answer (Rav Mesharshiya): People used to store Terumah in the same place that Sifrei Torah were kept, for both of them are Kodesh;

The Terumah [attracted mice, which] caused Seforim to be ruined - they decreed Tum'ah on Seforim [to discourage the practice].

(Mishnah): [Stam] hands.

Question: Why was this decreed?

Answer: Hands touch many things (Rashi - perhaps they will touch filth and debase Terumah; alternatively - perhaps they touched Tum'ah).

(Beraisa): Even hands that touched a Sefer Posel Terumah, on account of R. Parnach's teaching:

(R. Parnach): One who holds [the parchment of] a Sefer Torah in his bare hand [not through a cloth] will be buried bare.

Objection: This is unreasonable!

Correction: Rather, he will be buried bare of Mitzvos.

Objection: This is unreasonable!

Correction: Rather, he will be buried bare of that Mitzvah (of learning in it).

Question: Which of these two decrees was first?

We cannot say that the decree on Stam hands was first - if so, there would be no need to decree on hands that touched a Sefer!

Answer: The decree on hands that touched a Sefer was first.

(Mishnah): A Tevul Yom.

Objection: This is not a decree, he is Posel Terumah mid'Oraisa - "U'Va ha'Shemesh v'Taher"!

Correction: We must delete Tevul Yom from the Mishnah.

(Mishnah): Food that became Tamei through liquids.

Question: What kind of liquids were Metamei the food?

Suggestion: The liquids touched a Sheretz.

Rejection: If so, the food is Posel Terumah mid'Oraisa!

Answer: The liquids touched [Stam] hands - this is a decree on account of liquids that touched a Sheretz.

(Mishnah): Vessels that became Tamei through liquids.

Question: What kind of liquids were Metamei the vessels?

Suggestion: They are fluids of a Zav (spit, urine...)

Rejection: If so, the vessels are Posel Terumah mid'Oraisa!

"V'Chi Yarok ha'Zav ba'Tahor" - if a Zav spits on something the Tahor holds, he is Metamei it.

Answer: The liquids touched a Sheretz - this is a decree on account of fluids of a Zav.

Question: We said that these decrees were made when Beis Shamai outnumbered Beis Hillel - but Hillel and Shamai themselves decreed about hands, not their Talmidim!

(Beraisa): Yosi ben Yo'ezer and Yosi ben Yochanan decreed Tum'ah on Chutz la'Aretz and on glass vessels;

Shimon Ben Shetach enacted [a lien on all a man's property to pay a] Kesuvah and decreed Tum'ah on metal vessels (this will be explained);

Hillel and Shamai decreed Tum'ah on [Stam] hands.

Suggestion: Perhaps this means, Hillel and his followers and Shamai and his followers decreed.

Rejection: Rav Yehudah taught that there was an argument about all 18 things decreed - Hillel and Shamai argued about only three things [and Tum'ah of hands was not among them]!

(Rav Huna): Hillel and Shamai argued about three things and nothing else.

Suggestion: Perhaps Hillel and Shamai decreed to Toleh Terumah touched by Stam hands, and their Talmidim decreed to burn it!

Rejection: Ilfa taught that the initial decree regarding [Terumah that touched Stam] hands was to burn it.

Answer: Hillel and Shamai decreed about Terumah touched by Stam hands, the decree was not accepted; their Talmidim decreed, the decree was accepted.

Question: Shlomo decreed this [long before Hillel and Shamai]!

(Rav Yehudah): When Shlomo decreed Eiruvin and Netilas Yadayim, a Bas Kol (voice from Shamayim) said "Beni Im Chacham Libecha Yismach Libi Gam Ani" and "Chacham Beni v'Samach Libi va'Ashivah Chorfi Davar".

Answer: Shlomo decreed regarding Kodshim, they decreed regarding Terumah.