Responsa for Nedarim 55:12
תנא מתניתין בנדר להודיעך כחן דבית שמאי תנא ברייתא בשבועה להודיעך כחן דבית הלל
R. Huna said: A Tanna taught: Beth Shammai maintain: He must not volunteer with an oath; Beth Hillel say: He may volunteer even with an oath. Now, in the view of Beth Shammai, only with an oath may he not volunteer, but he may volunteer a vow. But we learnt: BETH SHAMMAI RULE: THE OWNER MUST NOT VOLUNTEER TO VOW. Moreover, he may merely not volunteer an oath, but he may vow with an oath [if requested]; but we learnt, BETH SHAMMAI MAINTAIN: ONE MAY MAKE ANY FORM OF VOW, EXCEPTING THAT SUSTAINED BY AN OATH? — The Mishnah deals with a vow, to shew how far-reaching is Beth Shammai's ruling;<span class="x" onmousemove="('comment',' I.e., one may not volunteer even a vow, which is not as grave as an oath. ');"><sup>8</sup></span>
Teshuvot Maharam
A. Whether or not one has taken an oath not to clip coins, the doing so is a serious crime, the perpetrators of which deserve severe punishment. Clipping coins is tantamount to stealing and robbing, and robbing Gentiles is a crime. Furthermore, such an act creates a public nuisance as it may result in causing great injury to other Jews innocently passing on these coins. It may even cause widespread disaster, and has already led to a great deal of bloodshed. Thus, clipping coins brought about the destruction of our brethren in France and Britain. In addition to committing a basic crime, these Jews broke their solemn oath to the burghers. Mental reservations do not invalidate an oath occasioned by legal circumstances. The talmudic ruling (Ned. 28a) that a person may invalidate his oath to extortionists and murderers by mental reservations, does not apply in this case; for, while extortionists and murderers, by administering an oath, strive to bolster their criminal purposes, it is legal and proper for a king or civil authority to forbid the clipping of coins. Therefore, their oath to the burghers was valid despite their mental reservations. Moreover, when the Gentiles will learn that the Jews clipped coins despite their oath — and they are bound to discover it sooner or later — they will suspect the Jews of wilfully breaking their oath. Should the latter inform the Gentiles that they disregarded their oath because of mental reservations, the consequences might be still more serious; for Gentiles will never again believe a Jew under oath. Therefore, if your authority and my authority carry enough weight, these Jews should be properly flogged.
This Responsum is addressed to: "My teacher Rabbi Judah."
SOURCES: L. 246; Mordecai Hagadol, p. 337c.