Gigul Shavua, גִלְגוּל שָׁבוּעָה TB Kidushin 27-8

Dappim TB Kidushin 27-8 provides is the source for a reoccurring principle throughout the Talmud. Once a person has to take an oath, another oath may be administered on top of the first. This is called in Hebrew gigul shavua, גִלְגוּל שָׁבוּעָה.

The source in the Torah allowing gilgul shavua is derived from the oath that the sota, a woman who is suspected of adultery, has to make.

“Ulla says: From where is it derived from the Torah that one can impose the extension of an oath, i.e., if one is required to take an oath for one claim, the other party can obligate him to take an oath with regard to other claims which on their own would not lead to the imposition of an oath?

“As it is stated with regard to a sota: “And the woman shall say: Amen, amen” (Numbers 5:22), and we learned in a mishna (Sota 18a): Concerning what does she say the double expression of: Amen, amen? She says amen on the curse, as she accepts the curse upon herself if she is guilty, and amen on the oath, as she declares that she is not defiled. She states: Amen if I committed adultery with this man about whom I was warned, amen if I committed adultery with another man. Amen that I did not stray when I was betrothed nor after I was married, nor as a widow waiting for my yavam to perform levirate marriage, since a woman at that stage is prohibited from engaging in sexual intercourse with any men, nor when married through levirate marriage to the yavam.” (Sefaria.org translation)

The rabbis learn that we can extend this principle to monetary cases as well from a kal vekhmer, a fortiori inference. “The school of Rabbi Yishmael taught that this can be derived through an a fortiori inference: And just as in the case of a sota, where an oath cannot be imposed by one witness, as two witnesses must testify that the wife secluded herself with the man concerning whom she was warned in order for her to be obligated to take the oath of a sota, and yet one can extend her oath, is it not logical that with regard to a claim involving money, where an oath can be imposed by the testimony of one witness, that one can extend the oath?” (Sefaria.org translation)

We can even apply this principle to an uncertain claim. What is an example of an uncertain claim? Two people want to dissolve their partnership and one says to the other, “You take care of all the details.” After all the paperwork, so to speak, is completed, the one who allowed his former partner to take care of all the details wants to make sure that the partnership was divided 50-50. He doesn’t know for sure whether his former partner cheated him or not. Perhaps there is a fear that his partner took more than 50% rationalizing that he did all the work, so he’s entitled to more than 50% of the proceeds. This is an uncertain case because the first partner just doesn’t know whether or not his partner has divided the partnership equally.

“The Gemara asks: We found a source for the extension of an oath in the case of a definite claim, i.e., when the plaintiff is certain of his claim. From where do we derive that this halakha of the extension of an oath applies also to uncertain claims, when the plaintiff is not sure the defendant owes him money but merely suspects this to be the case?

“The Gemara answers: It is taught in a baraita that Rabbi Shimon ben Yoḥai says: The Torah states an external oath, i.e., an oath administered outside of the Temple, and it states an internal oath, an oath administered inside the Temple courtyard, i.e., the oath of a sota. Just as with regard to an oath stated in the Torah that is taken inside the Temple, the Torah rendered uncertainty like certainty, as in the case of a sota the husband’s claim is based on suspicion and yet he can extend that oath; so too, with regard to an oath stated in the Torah that is taken outside the Temple, the Torah rendered uncertainty to be like certainty, i.e., all oaths can be extended to include even uncertain claims.” (Sefaria.org translation)

Finally the Gemara sets limits what kind of oaths may be limited to. One may not impose a frivolous oath whose sole purpose is to denigrate the person. “…the court ostracizes one who says this to another, as it is taught in a baraita: One who calls another a (Canaanite-gg) slave (when it is well-known that he is a free Jew-gg) shall be ostracized. One who calls another a mamzer (a person born of an incestuous relationship. According to Jewish law a child born out of wedlock isn’t a mamzer.-gg) incurs the punishment of forty lashes. If one calls another a wicked person then the insulted person may harass him in all aspects of his life. In light of this halakha, it is clear that the court will not force the accused to respond to this insult by taking an oath.” (Sefaria.org translation)