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.
It is possible to liken a situation wherein life endangerment overrides the Sabbath to one in which a positive commandment overrides a negative one. Nothing prohibits one from entering a situation where a positive commandment overrides a negative one.
According to the laws of inheritance, when a person expires, his children inherit his assets, and the firstborn receives a double portion. But what if the heir proclaims, "My firstborn shall not receive double," or, "My son shall not inherit me"?
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.
One must be on guard against the prohibition of "gnevat da'at," or deception. For example, it is forbidden to use an expression like, "I am opening this bottle of wine in your honor," when, in truth, you had at any rate intended to open the bottle.