Nedarim 28A

חוץ מבשבועה. ובית הלל אומרים: אף בשבועה.

except for by taking of an oath, due to its more stringent nature. And Beit Hillel say: One may mislead them even by taking an oath.

בית שמאי אומרים: לא יפתח לו בנדר, ובית הלל אומרים: אף יפתח לו. בית שמאי אומרים: במה שהוא מדירו. ובית הלל אומרים: אף במה שאינו מדירו.

Beit Shammai say: When negotiating with a robber, one should not initiate by taking a vow for him unless the robber does not believe his claim, in which case he may take a vow to reinforce his words. And Beit Hillel say: He may even initiate by taking a vow to him. Beit Shammai say: One may take a vow only about that which the robber compels him to take a vow but may not add to it. And Beit Hillel say: One may take a vow even about that which he does not compel him to take a vow.

כיצד? אמר לו: אמור ״קונם אשתי נהנית לי״, ואמר: ״קונם אשתי ובני נהנין לי״, בית שמאי אומרים: אשתו מותרת ובניו אסורין. ובית הלל אומרים: אלו ואלו מותרין.

The Mishnah explains the previous statement: How so? If the extortionist said to him that he should say: Benefiting from me is konam for my wife if the vow is not true, and he said: Benefiting from me is konam for my wife and my children, Beit Shammai say: His wife is permitted to benefit from him, since the extortionist demanded that he take that vow, but his children, whom he added of his own accord, are prohibited from benefiting from their father. And Beit Hillel say: Both these and those are permitted to benefit from him.

גמ׳ והאמר שמואל: דינא דמלכותא דינא?

Talmud: The Talmud asks, concerning the Mishnah’s statement that one may take a vow to tax collectors: But didn’t Shmuel say: The law of the kingdom is the law, i.e., there is a halakhic principle that Jews must obey the laws of the state in which they live? Since one must pay the tax determined by the kingdom, how did the rabbis permit one to lie in order to avoid paying?