Question: (The Beraisa mentioned "years of a boy or girl.") What are they?

Answer #1 (Rav Gidal citing Rav): They are the years of Erchin. (One who pledges Ploni's Erech must give Hekdesh a sum of money based on Ploni's age and gender.)

Answer #2 (Rav Yosef): They are the years of the exception of our Perek. (Regarding Seris and Ailonis, the Mishnah does not say "and a day ")

Abaye (to Rav Yosef): Do you argue with Rav Gidal (about the Halachah)?

Rav Yosef: No. Both of these must be full years. (We argue only about what the Beraisa refers to.)

Support: Rav Gidal cited Rav. He must agree that the years of Seris and Ailonis are full, for Rav said that all years mentioned in our Perek are full!

Question: Why didn't Rav Gidal say that "boy or girl" refers to Seris and Ailonis?

Answer: Presumably, it is like everything else in the Beraisa, for which the years are explicit in the Torah.

Question: Why didn't Rav Yosef say that the Beraisa refers to Erchin?

Answer: If so, it should have said "Zachar Oh Nekevah," like it says in Parshas Erchin.

(R. Yitzchak bar Nachmani citing R. Elazar): The Halachah follows R. Yosi ben Kipar.

R. Zeira longed to go to Eretz Yisrael to hear this directly from R. Elazar. (He went.)

R. Elazar: I said that presumably the Halachah follows R. Yosi. Since this is the only Mishnah in our Perek that does not mention the extra day, presumably full years are not required.

(Mishnah): If the lower Siman (two hairs) came before the upper Siman (breast development), she may do Yibum or Chalitzah. (She definitely became a Na'arah.)

R. Meir says, if the upper Siman came before the lower Siman, even though this is impossible (this will be explained), she may not do Yibum or Chalitzah yet;

Chachamim say, she may do Yibum or Chalitzah, for the lower Siman can come before the upper Siman, but not vice-versa.

(Gemara) Question: If R. Meir says that it is impossible for the upper Siman to come before the lower Siman, why does he give the law when this happens?!

Answer: He means that according to Chachamim it is impossible. He holds that it is possible.

Question: The Mishnah need not mention that it is impossible according to Chachamim. It suffices to teach the argument, and we will realize that Chachamim permit Chalitzah because they hold that the lower Siman always comes first!

Answer: If so, one might have mistakenly explained as follows:

(All agree that) the lower Siman usually comes first;

In general, R. Meir is concerned for the minority. Also here, perhaps the upper Siman came first!

In general, and also here, Chachamim rely on the majority.

We would say that the Mishnah discusses when we did not check for hairs. However, if a girl brought the upper Siman and we checked for hairs and did not find them, all would agree that she is from the minority, and still a minor;

Therefore, Chachamim explicitly say (in the Mishnah) that this is impossible. She definitely had hairs. They must have fallen out.

Question: According to R. Meir, we understand "Shadayim Nachonu u'Se'arech Tzime'ach" (the upper Siman can precede the lower). According to Chachamim, this is impossible!

Answer: They explain that because the upper Siman was seen, we know that the lower Siman came.

Question: According to R. Meir, we understand "b'Asos mi'Mitzrayim Dadayich Lema'an Shedei Ne'urayich" (the upper Siman came, but you were not yet a Na'arah). According to Chachamim, this is impossible!

Answer #1: Because the upper Siman was seen, clearly you were a Na'arah.

Answer #2: The entire verse discusses the upper Siman. Hash-m rebukes Yisrael (and compares Yisrael to an immoral girl):

When your upper Siman started to come, you did not retract (Metzudas David - from the idolatry you did in Mitzrayim). When it was complete, you still did not retract!

Question: All agree that we rely on the lower Siman. What is the source?

Answer: They expound like Rav Yehudah:

(Rav Yehudah (and Tana d'Vei R. Yishmael)): "Ish Oh Ishah Asher Ya'asu mi'Kol Chatos ha'Adam" equates men and women regarding all punishments;

Just like a man is established to be an adult through one Siman (pubic hairs are his only Siman), also a woman.

Question: Perhaps either Siman establishes a woman to be an adult!

Rejection: Just like a man is established only through the lower Siman, also a woman.

Support (Beraisa - R. Eliezer bar Tzadok): Once the lower Siman comes, we are not concerned for the upper Siman.

(Beraisa - R. Shimon ben Gamliel): In big cities, the lower Siman comes before the upper Siman (so we may rely on the upper Siman);

In villages, (due to the labors in which the girls engage) the upper Siman comes before the lower Siman (so we may not rely on it);

R. Shimon ben Elazar says, the right breast is not a reliable Siman in rich girls (it is affected by their garments), and the left is not reliable in poor girls (due to certain chores).

(Beraisa): The left breast develops before the right one.

(R. Chaninah): There was only one known instance of the left developing before the right.

(Beraisa): Simanim of girls are always checked by women;

R. Eliezer would ask his wife to check girls. R. Yishmael would ask his mother.

R. Yehudah permits women to check before and after the Perek (the 12th year). They may not check during the Perek itself. A girl may not rely on checking of women to (do Mi'un or Chalitzah and) marry;

R. Shimon says, women may check even during the Perek itself.

A woman is believed (about a girl she checked) to be stringent, but not to be lenient:

She is believed to say that a girl is an adult and hence may not do Mi'un. she is believed to say that a girl is a minor and hence may not do Chalitzah yet.

She is not believed to say that the girl is a minor to allow Mi'un, nor to say that she is an adult to allow Chalitzah (unless a Chazakah based on the girl's age supports her).

(Beraisa - R. Yehudah): Women check her before and after the Perek.

Question: We understand why they check her before. If they find hairs, we will know that they are Shuma, so we will not establish her to be an adult after the Perek due to these same hairs;

However, why do they check her after the Perek?

(Rava): We need not check a girl above 12. She is Muchzekes to be an adult.

Answer: Rava's Chazakah forbids Mi'un. (Even if we do not find hairs, we are concerned lest they came and fell out.) We must check her to allow Chalitzah. (Eshel Avraham 55:7 - we do not rely on this Chazakah for mid'Oraisa laws, for it is easy to verify, and a sizable minority do not get Simanim until later.)

(Beraisa - R. Yehudah): Women do not check her during the Perek.

He holds that during the Perek is like after the Perek, i.e. hairs make her an adult;

After the Perek she is believed (that she found hairs), for this merely confirms Rava's Chazakah;

During the Perek she is not believed (that she found hairs), for Rava's Chazakah does not apply.

(Beraisa - R. Shimon): Women check her during the Perek.

He holds that during the Perek is like before the Perek, i.e. hairs do not make her an adult;

We check for hairs (Shuma), lest we use these same hairs to establish her to be an adult after the Perek.

(Beraisa): A woman is believed to be stringent, not to be lenient:

Question: Who taught this clause?

Answer #1: R. Yehudah taught it. He refers to checking during the Perek.

Answer #2: R. Shimon taught it. He refers to checking after the Perek;

(Tosfos - it is possible that) he argues with Rava (and holds that there is no Chazakah. R. Shimon requires men to permit a girl to do Chalitzah. He explicitly says (52b) that even hairs on fingers are a Siman. Men could see this. The Beraisa meant that only women check girls for hairs in all possible places, i.e. including the Ervah. Mordechai (Yevamos 12:58-59) - some say that it suffices if she is Muchzekes among her neighbors to be a Gedolah. Sefer ha'Terumos says that there is no disgrace for men to check the upper Siman. Others rely on women (Beis Shmuel - after the Perek). Tosfos - if it is obvious from her appearance that the upper Siman came, there is no need to check.)