Temporary Townsmen and Walled-City Dwellers on Purim
The sages instituted a number of days for the reading of the Scroll of Ester. The Mishnah introduces the novel concept that there are situations in which a walled-city dweller reads on the fourteenth and a townsman reads on the fifteenth.
The opening Mishna of tractate Sanhedrin states: A slanderer [is judged] by three - these are the words of R. Meir; the Sages say, a slanderer [is judged] by twenty-three, because such [an offense] involves capital punishment.