Megillah, Chapter 4, Mishnah 1. This Mishnah continues to deal with the laws of reading the Megillah, and from there moves on to the laws of reading the Torah.
How the Megillah is read:
"Hakorei es haMegillah omed v'yoshev" - one who reads the Megillah of Esther may stand or sit as he wishes, and he is not obligated to stand.
"Kara echad, ke'ra'uha shnayim - yatz'u" - whether one person reads the Megillah or two people read it at one and the same time, the listeners have fulfilled their obligation.
At first glance this is a novel ruling, for we have a principle that two voices cannot be heard as one. The answer is that the reading of the Megillah is exceedingly beloved to those who hear it, and because of that affection they are able to concentrate and listen to one reader even while his fellow is reading along with him.
"A place where they were accustomed to recite a berachah":
"Makom shenahagu l'varech - y'varech, v'shelo l'varech - lo y'varech" - the matter depends on the custom of the place. Which berachah is the Mishnah speaking about? The Gemara explains that it refers to the berachah recited after the Megillah, "HaRav es riveinu", since everyone recites the berachah beforehand. Like every mitzvah, which requires a berachah before it is performed, and for the reading of the Megillah three berachos are recited beforehand: "al mikra megillah", "she'asah nissim" and "shehecheyanu". The only question concerns the berachah afterward, and it is recited when the reading takes place with a minyan.
The Torah reading on Monday, Thursday and Shabbos at Minchah:
"B'sheni uv'chamishi uv'Shabbos b'minchah korin sheloshah, ein pochasin mehen v'ein mosifin aleihen" - three people are called up to the Torah on these days, no fewer than three and also no more than that. And the reason is:
On Monday and Thursday: these are workdays, and one should not burden the community with a lengthy Torah reading.
On Shabbos at Minchah: it is a time close to nightfall, and that too is a time when it is not fitting to hold a lengthy reading. Rashi explains that the community was occupied with learning the entire day, and therefore does not want a lengthy Torah reading at that hour.
The Mishnah adds: "Ein maftirin b'navi" - for the same reason the Sages did not institute a Haftarah on Monday, Thursday and Shabbos at Minchah, so as not to add to the burden on the community.
"The one who opens and the one who concludes recite a berachah on the Torah":
The first person called up, who opens the Torah reading, recites the berachah before it, and the last one called up, who concludes the reading, recites the berachah after it. Such was the law in the days of the Mishnah: only the first recited the berachah before, and only the last recited the berachah after.
In the days of the Gemara the Sages instituted the practice we follow today, that each and every person called up recites a berachah before and a berachah after. The reason for this enactment is a decree on account of those who come in and those who leave: someone who enters the shul late will not hear the berachah before the reading, and someone who leaves early will not hear the berachah after it, and they are liable to think that there is no berachah before the Torah or after it. So that everyone should see that there is a berachah before and after, the Sages instituted that each and every one recite a berachah before his reading and a berachah after it.
In summary: in this Mishnah we learned that the Megillah may be read standing or sitting, by one reader and even by two reading together - because of how beloved the reading is; that the berachah after the Megillah depends on the custom of the place, while the three berachos before it are recited everywhere; and that on Monday, Thursday and Shabbos at Minchah only three are called up and no Haftarah is read, because of the burden on the community. We also learned that in the days of the Mishnah the one who opened recited the berachah before and the one who concluded recited the berachah after, while in the days of the Gemara the Sages instituted that each person called up recite a berachah before and after, a decree on account of those who come in and those who leave.