Arachin 3a — ערכין ג.

It includes women. Rashi explains that the Megillah is an obligation for them too, and a woman may read it, even for men. Tosafot bring the Bahag, who reads a Tosefta to say that women are obligated only to hear it, and conclude that a woman reads for other women but not for men.

This follows Rabbi Yehoshua ben Levi, who says in Masechet Megillah 4a that the reading of the Megillah binds women as well, since they too were saved in that miracle. The Rambam (1:1) and the Shulchan Aruch (689:1) rule that everyone is obligated, men and women. The Shulchan Aruch adds (689:2) that some say women do not read for men.

The next Mishnah opens with "everyone": everyone is obligated in zimun, the invitation that (at least) three people who ate together say before Birkat HaMazon. Who does "everyone" include?

It includes women and slaves. A baraita teaches that women make a zimun among themselves, and slaves make a zimun among themselves. Rashi explains that three women, or three slaves, may join for a zimun of their own, but two women or two slaves do not join with men to make up three. His reason is that the wording of Birkat HaMazon does not fit them equally: women do not say "Your covenant" (the brit milah), and slaves do not say "the land You gave our fathers as a heritage." Tosafot read this zimun as permission, not a duty. Their proof is Berachot 45b, where women make a zimun "if they wish," and they write that this is what our women rely on when they do not make a zimun. See the Rambam (Hilchot Berachot 5) and the Shulchan Aruch (Orach Chayim 199).

Everyone joins to make up the three for a zimun. Who does that come to include?

A child who knows to Whom we bless, who understands that the berachah is said to Hashem. Rav Nachman says that such a child is counted for a zimun; he says it in Berachot 48a as well. Tosafot add that we do not rule this way. They bring the Yerushalmi, where Rabbi Yose ben Halafta says he ate with his father, Halafta, many times and was not counted for a zimun until he showed the signs of physical maturity.

Everyone becomes tamei through zivah. A zav is a man with a discharge (not seminal) that the Torah makes a source of tumah (impurity), in Parshat Metzora. Who does "everyone" come to include?

A baby boy one day old. Even he can become a zav.

A baraita gives the source. The pasuk opens with "ish ish," a man, a man. Why say "man" twice? To include a baby one day old, who also becomes tamei through zivah. These are the words of Rabbi Yehuda. Tosafot ask why the Gemara did not quote the Mishnah in Niddah 43b, which states this outright. They answer that the baraita also shows where it comes from.

Rabbi Yishmael, the son of Rabbi Yochanan ben Beroka, says the doubled word is not needed for the baby.

At the end of the same parsha the Torah says "the zav, for male and for female." Male means any male, young or old; female means any female, young or old. So the baby is already included.

Then why does the Torah say "ish ish"? The Torah used the ordinary speech of people. Saying a word twice is how people talk, and no law is learned from it.

Everyone becomes tamei through tumat met, contact with a dead body. Who does that come to include?

It includes a child. We might have thought he is left out, since in Parshat Chukat the Torah speaks of "a man who becomes tamei and does not purify himself": a man, and not a child.

So the Mishnah teaches that he is included. In the same parsha the mei chatat, the water mixed with the ashes of the parah adumah, is sprinkled "on the persons who were there," every person, a child as well.

Then what does the word "man" come to exclude?

It leaves the child out of karet (Being “cut off” a biblical punishment administered directly by Heaven rather than by a human court). Rashi explains that this pasuk is about one who enters the Beit HaMikdash while tamei, who is punished with karet. A child is not punished, but he is tamei like an adult, and he makes food and drink tamei. Tosafot ask why a pasuk is needed, since a child is never punished. They answer that once the Torah included him in tumah, we might have thought he is included in karet as well.

Everyone becomes tamei through nega'im, the marks of tzaraat. Who does that include?

A child. We might have thought he is left out, since in Parshat Tazria the Torah says "he is a man with tzaraat": a man, and not a child. So the Mishnah teaches that he is included.

The Gemara asks: why not say that a child really is left out?

Because the Torah opens the laws of nega'im with "a person (adam), when a mark appears on his skin." Adam covers everyone, young or old (like Adam, the first human, it includes all “humans”).

Then why does the Torah need the word "man"?

For what a baraita teaches. "Man" tells me only about a man; where do we learn a woman? When the next pasuk says "and the metzora," that is a second word, and it comes to include the woman.

If so, what does "man" come to teach?

It belongs to the law right below it. A man with tzaraat lets his hair grow wild and tears his garments; a woman does not. Tosafot explain that for a woman this would be a disgrace.

Everyone may look at nega'im; everyone is fit to look at nega'im. Rashi and Rabbeinu Gershom explain that these are one teaching, which was learned in two places in two forms. Who does it come to include?

It comes to include a Kohen who does not know the marks and their names well.

But a teaching in Shevuot 6a says that a Kohen who does not know them and their names may not look at nega'im!

Ravina answers that there is no contradiction. Here, they explain the marks to him and he understands; there, they explain and he still does not understand. Rashi describes the practice that a talmid chacham who knows the laws goes with the Kohen and tells him "say tamei" or "say tahor," and the Kohen says it, because only the Kohen's word makes the person tamei or tahor.

Everyone is fit to mekadesh the parah adumah, mixing its ashes into the spring water. Who does that include?

For Rabbi Yehuda it comes to include a child; for the Chachamim it includes a woman.

The source is the Mishnah in Parah 5. everyone is fit to do this except a cheresh, a shoteh and a katan. Rabbi Yehuda allows a child and disqualifies a woman and an androgynous. Rashi points to Yoma 43a, where the reason of each side is explained.

Everyone is fit to sprinkle the mei chatat on a person who is tamei. Who does that include?

It comes to include an arel, a man who is not circumcised. Rashi gives the following case, that his brothers died because of their milah, so as a precaution, he is not circumcised. As Rabbi Elazar says in Yevamot 72b, when an arel sprinkles (the ashes mixed with water), the sprinkling counts. The reason given there: he is like a tevul yom, who may not eat terumah but is fit for the work of the parah adumah.

Everyone may slaughter. Who does that include?

Rashi notes that two Mishnayot open with "everyone slaughters," in Chullin 2a and Chullin 15b. One includes a Kuti, a Samaritan, and the other includes a Jew who is a mumar (a Jew who breaks a Torah law for his own appetite, not to defy the Torah). Rabbeinu Gershom explains that this means a mumar for one matter. The Gemara discusses both in Chullin 3a.

Everyone can make the household move up to Eretz Yisrael, as the Mishnah in Ketubot 110b teaches. Who does that include? The answer opens the next amud.