Answer: Rather, R. Akiva expounds four verses. They teach the Isurim to her husband, the Bo'el, Terumah, and Kehunah;

R. Yishmael does not need a verse for Kehunah. He learns from a Kal va'Chomer from Terumah.

Question: (The verses do not specify what they forbid.) Perhaps the verse teaches about Kehunah, but she is permitted to Terumah!

Answer: It is more reasonable that the third verse teaches an Isur similar to the Isurim to the husband and the Bo'el, which apply in the husband's lifetime (she is forbidden to the Bo'el even if her husband divorces her), i.e. Terumah. (An Isur to) Kehunah applies only after the husband dies. (Only death of her husband could permit her to Kohanim.)

R. Akiva holds that the Isurim need not resemble each other;

Alternatively, he holds a verse teaches the Isur to Kehunah, even though it could be learned from a Kal va'Chomer.

(Rav Gidal): Different verses distinguish between whether or not a party has understanding!

"If meat (of Korbanos) touches anything Tamei, it will not be eaten" - if it became Vadai Tamei, it may not be eaten. If it is a Safek, it may be eaten;

Contradiction: "Every Tahor person may eat meat (of Korbanos)" - if he is Vadai Tahor, he may eat. If he is Safek, he may not eat;

Resolution: When an involved party has understanding, we are stringent about a Safek. When no involved party has understanding, we are lenient.

It is necessary to learn both like Rav Gidal and from Sotah.

If we only learned like Rav Gidal, we would not distinguish between a Reshus ha'Yachid and a Reshus ha'Rabim.

If we only learned from Sotah, we would think that we are stringent only when both the party that becomes Tamei and the party that is Metamei have understanding.

(Mishnah): On that day, R. Akiva expounded "every earthenware Kli..."

Question: (According to R. Yochanan ben Zakai,) if no verse says that Terumah can become a Shlishi (third level Tum'ah), why can it become a Shlishi?

Answer (Rav Yehudah): No verse teaches this, but a Kal va'Chomer does.

Suggestion #1: A Tvul Yom (a person or Kli who immersed from Tum'ah today) is Tahor regarding Chulin (he does not Metamei it), but he disqualifies Terumah by touching it. A Sheni loaf is Tamei regarding Chulin. All the more so, it disqualifies Terumah by touching it!

Objection: One cannot learn from a Tvul Yom, for (before immersing) he was an Av ha'Tum'ah (he could be Metamei people and Kelim). The loaf was not an Av ha'Tum'ah!

Suggestion #2: We learn from a Tvul Yom who touched a rodent (even before immersing he was not an Av ha'Tum'ah).

Objection: One cannot learn from a Tvul Yom, for he (or it) can be an Av ha'Tum'ah.

Answer: We can learn from an earthenware Kli, since it can never be a source of Tum'ah.

Objection: We cannot learn from an earthenware Kli, since it has the stringency that it becomes Tamei from (Tum'ah in) its airspace!

Answer: We learn from a Tvul Yom (it is Metamei Terumah even though it lacks this stringency).

The stringencies of a Tvul Yom and of an earthenware Kli are different. The Tzad ha'Shavah (what is common to both of them) is that they are Tahor regarding Chulin, and are Metamei Terumah. All the more so, a loaf that is a Sheni is Metamei Terumah. (Rashi's text - the Tzad ha'Shavah is that they are called Tamei, and they are Metamei Terumah. Also a Sheni loaf is Metamei Terumah! Our text is difficult, for a Tzad ha'Shavah always cites the stringencies of the sources. Also, an earthenware Kli that is Metamei Terumah is also Metamei Chulin!)

R. Yochanan ben Zakai was concerned lest future Chachamim reject the Kal va'Chomer because each source has a special stringency.

R. Yochanan ben Zakai holds that this is not grounds to reject a Kal va'Chomer.

(Beraisa - R. Yosi): We learn that Kodshim can become a Revi'i (fourth degree Tum'ah) from a Kal va'Chomer:

A Mechusar Kipurim (a Tamei person who needs to bring a Korban, and has completed his Taharah process except for the Korban) may eat Terumah, but he disqualifies Kodshim. Food that is a Shlishi is forbidden by Terumah, all the more so it disqualifies Kodshim!

A verse teaches that Kodshim can become a Shlishi. The Kal va'Chomer teaches that it can become a Revi'i.

Question: Which verse teaches that Kodshim can become a Shlishi?

Answer: "If meat touches anything Tamei, it may not be eaten" - even if it touched a Sheni.

Objection (R. Yochanan): I do not understand R. Yosi. There is an obvious refutation of his Kal va'Chomer!

If a Tvul Yom touched a food, even though the food is Tamei regarding Terumah, it does not make a Revi'i in Kodshim!

(Beraisa - Aba Sha'ul): A Tvul Yom is like a Rishon regarding Kodshim. He is Metamei two (levels of) Kodshim foods (what he touches directly (level 1, it is a Sheni), and what touches what he touched (level 2, a Shlishi)) and disqualifies a third (what touches level 2. It is a Revi'i. It may not be eaten, but it cannot disqualify another food);

R. Meir says, he is Metamei one (makes it a Shlishi), and makes a second (level) Pasul (a Revi'i);

Chachamim say, just like he is Posel food and drink of Terumah, he is Posel food and drink of Kodshim (the first level cannot disqualify another food).

Objection (Rav Papa): The question assumes that R. Yosi holds like Chachamim. Perhaps he holds like Aba Sha'ul (or R. Meir)!

Answer: He cannot. If he did, he would learn a fourth degree of Tum'ah in Kodshim from a food that a Tvul Yom touched.

A Tvul Yom is Tahor regarding Chulin, yet he disqualifies (mid'Oraisa) two more levels of Kodshim foods. A Sheni is Tamei regarding Chulin, all the more so it disqualifies two more levels of Kodshim!

Suggestion: Perhaps he holds that we cannot learn from a Tvul Yom, for a Tvul Yom can be an Av ha'Tum'ah.

Rejection: He learns from a Mechusar Kipurim, even though a Mechusar Kipurim can be a source of Tum'ah!