Nedarim, Chapter Three, Mishnah Four
This mishnah discusses the second types of forced vows, those made under coercion. While all rabbis agree that one is allowed to make a false vow in order to protect oneself or ones property, Beth Shammai and Beth Hillel disagree with regard to some of the details.
1) One may vow to murderers, robbers, or tax collectors that it [the produce which they demand] is terumah, even if it is not; [or] that it belongs to the royal house, even if it does not.
2) Beth Shammai says: one may make any form of vow, except an oath;
a) But Beth Hillel says: even an oath.
3) Beth Shammai says: he must not volunteer to vow;
a) Beth Hillel says: he may do so.
4) Beth Shammai says: [he may vow] only as far as he makes him vow;
a) Beth Hillel says: even in respect of what he does not make him vow.
i) How so?
ii) If they said to him, say: Konam be any benefit my wife has of me, and he said, Konam be any benefit my wife and children have of me,
(1) Beth Shammai says: his wife is permitted, but his children are forbidden;
(2) Beth Hillel says: both are permitted.
Section one: One is allowed to make a false vow that ones produce is terumah in order to prevent it from being taken away. What is strange here is that the mishnah assumes that while someone might be willing to murder, rob or illegitimately collect taxes, he will not take terumah. Indeed, this is truly hard to imagine; after all, what worse crime is there than murder. Albeck explains that the terumah vow refers only to tax collectors, who would not collect taxes from terumah. He refers to Josephus who says that the Romans allowed terumah to be exempt from taxes.
The second false vow referred to is stating that the property belongs to the king. Indeed, it is easier to imagine a murderer or robber fearing taking property that belongs to the king.
Section two: The mishnah now begins a series of debates between Beth Shammai and Beth Hillel.
Beth Shammai holds that since oaths are more consequential than vows, one may not make a false oath, even under this type of coercion. Beth Hillel says even false oaths may be made.
Section three: Beth Shammai says that one may not initiate taking the vow. If the murderer or robber did not ask the person to vow that the produce was terumah or belonged to the king, then he should not. Beth Hillel says even if not asked, he may take a vow.
Section four: Beth Shammai says that the person should only vow exactly what was asked of him by the murderer/robber. If he, upon his own initiative, adds on to the vow, then that which he added has validity. Beth Hillel says he may add on, and just as his vow has no validity regarding that which the murderer/robber told to him to swear, so too the part he added has no validity.