Shevuot 25

On today’s daf, we get a new mishnah which further explains how oaths function and to what they can be applied:

An oath on an utterance may address both matters of substance and insubstantial matters.

The mishnah gives some clarifying examples of the second category — matters that are without substance:

“On my oath I will sleep,” or: “On my oath I will not sleep.” “On my oath I slept,” or: “On my oath I did not sleep.” Or: “I will throw a stone into the sea,” or: “I will not throw it,” or: “I threw it,” or: “I did not throw it.”

Sleeping is considered an insubstantial matter (“intangible” in the Steinsaltz translation) because it doesn’t involve a physical object. Throwing a stone into the sea is a different type of insubstantial: Rather than lacking materiality, it offers no clear benefit or detriment, and is “insubstantial” by virtue of its neutrality. 

In today’s Gemara, the rabbis pick up on this clause to discuss some of the distinctions between oaths and vows, since unlike oaths vows cannot take effect on an insubstantial matter.

The sages taught: There is a stringency that applies to vows and not to oaths, and there is a stringency that applies to oaths and not to vows. The stringency that applies to vows is that vows take effect with regard to a matter involving a mitzvah, like they take effect with regard to an optional matter, which is not the case with regard to oaths.

Vows, the rabbis assert, are more stringent (i.e., more powerful) than oaths in that they can prohibit matters about which a person is commanded. For example, someone can take a vow that sitting in the sukkah is prohibited to them, and such a vow would take effect, even though it contravenes a mitzvah from the Torah. If one took an oath not to sit in the sukkah, it would be ineffective. 

The manner in which oaths are more powerful than vows is that found in our mishnah:

The stringency that applies to oaths is that oaths take effect with regard to an insubstantial matter like they do with regard to a substantial matter, which is not the case with regard to vows.

Since vows take effect on things rather than people, they cannot take effect on intangible things; I can prohibit myself from sleeping, but I can not make “sleep” forbidden to me.

While this clause is the one connecting the discussion to our mishnah, the Tosafot (medieval commentators following the school of Rashi) delve into the complicated question of why vows can prohibit things that involve a mitzvah but oaths cannot. Ultimately they conclude that the primary distinction is the one just made in the mishnah: Vows take effect on things, whereas oaths take effect on people. Oaths, therefore, look something like this: I will not sleep, I will not eat, I will throw a stone in the sea. Vows, in contrast, take effect on things: Wine is forbidden to me, sex is forbidden to me, that cow is forbidden to me.

Within the Brisker method, a form of learning pioneered by Rabbi Chaim Solovetchik, such a distinction is generally referred to as cheftzah/gavrah. Cheftzah, which means “thing” or “object,” refers to when a status inheres in an object itself. When a person takes a vow that sitting in the sukkah is prohibited to them, the sukkah itself has become the prohibited object. Gavrah, meaning “person” or “man,” refers to the status that inheres in a person’s actions. When a person takes an oath not to sit in the sukkah, the thing that they’re attempting to prohibit is their action — not the sukkah itself.

This, the Tosafot explain, is why a vow can take effect to contravene a Torah commandment while an oath cannot. There is no commandment that a sukkah have a person sitting in it, only a commandment that people sit in a sukkah. Therefore, a prohibition on the sukkah — which would have to be a vow — can take effect. But I, as a person, am commanded to sit in the sukkah; therefore I cannot take an oath prohibiting myself from doing that which the Torah explicitly commands me to do.

Such a distinction may seem fine-grained, but this categorical differentiation can be applied to a number of sugyot throughout the Talmud, and can help explain differences in ruling on situations that are, at first glance, nearly identical, such as the prohibitions generated by vows and oaths.

Read all of Shevuot 25 on Sefaria.

This piece originally appeared in a My Jewish Learning Daf Yomi email newsletter sent on May 26, 2025. If you are interested in receiving the newsletter, sign up here.