Nedarim, Chapter 3, Mishnah 4. This Mishnah continues the subject of the previous one - vows made under duress. There we dealt with a person who took a vow and was unable to fulfill it because of circumstances beyond his control; here we deal with vows made under coercion, which are likewise beyond the control of the one who vows.
The text of the Mishnah:
"Nodrin la'harugin ve'lacharamin ve'lamochsin" - a person may take a vow before these three types of people, and the vow does not take effect:
Harugin - murderers, who threaten to take a person's life if he does not hand over his property to them.
Charamin - robbers who seize objects; although they are not actually murderers, they destroy and ruin a person's property if it is not handed over to them.
Mochsin - tax collectors who collect taxes unlawfully.
In the examples the Mishnah brings, the one taking the vow uses wording that presents his possessions as items the robber does not really want:
"Shehi Terumah af al pi she'eino Terumah" - the person vows that the food in his possession is Terumah. Terumah has a low market value, since it may be eaten only by kohanim who are tahor. Even though in reality it is not Terumah, he may tell them something untrue and even take a vow about it, and the vow does not take effect, because it was made under duress.
"Shehen shel beis hamelech af al pi she'einan shel beis hamelech" - the person says that the items belong to the king, even though in truth they are not his, since robbers do not want to get entangled with the king.
The dispute between Beis Shammai and Beis Hillel:
The wording of the vow: Beis Shammai say "Bakol nodrin chutz mibishvuah" - a person may free himself from them with any form of vow, but he should not resort to an oath, whose severity is far greater. Beis Hillel say "Af bishvuah" - he may free himself from these criminals even with an oath, and the oath does not take effect.
Initiating the vow: Beis Shammai say "Lo yiftach lo b'neder" - if they asked him to take a vow, he may do so, but he should not offer it on his own initiative. Beis Hillel say that he may even initiate and propose the vow himself.
Adding beyond what was demanded: Is the one vowing limited to the item he was pressed to vow about, or may he include in his vow items he was not pressed about as well? According to Beis Hillel, just as he may initiate the vow, so too he may add further details beyond what the robber asked for.
An example of this dispute:
The robbers tell a person to take a vow, in order to guarantee his words, that his wife will be forbidden to derive benefit from him if the items are not Terumah or the property of the king. Instead of mentioning only his wife, the one vowing says that his children too will not derive benefit from him, adding them on his own initiative.
According to Beis Shammai, his wife is permitted to him, since that is what was demanded of him and it falls under the category of vows made under duress; but his children are not included in vows made under duress, since he was not forced to add them. According to Beis Hillel, both are permitted: since he is allowed to include the children even though he was not pressed about them, the entire vow is considered a vow made under duress, and no prohibition results from it.
In summary: in this Mishnah we learned that one may take a vow before murderers, robbers and tax collectors, and these vows do not take effect, since they were made under duress; and that for this purpose a person may present his possessions as Terumah or as the property of the king, even though it is not true. We examined the three points of dispute between Beis Shammai and Beis Hillel: whether one may swear an oath, whether one may initiate the vow on his own, and whether one may add beyond what was demanded of him.