Shevuos, Chapter 3, Mishnah 5. This mishnah deals with the kinds of things and actions that an oath can take effect upon.
The four categories listed in the mishnah:
"echad devarim shel atzmo" - an oath about matters that concern the person himself, that he will perform a certain action or that he will not perform it.
"echad devarim shel acheirim" - an oath that concerns other people, as will be explained below.
"echad devarim she'yesh bo mamash" - an oath that takes effect upon a physical object, such as when a person forbids a particular item to himself.
"echad devarim she'ein bo mamash" - an oath that takes effect upon something that is not a physical entity but only an activity.
"Keitzad?" - the mishnah's examples:
For matters concerning others: "she'etein li'ploni v'shelo etein" - that he swore he would give a certain object to his fellow, or that he would not give it to him. "shenasati v'shelo nasati" - that he swore he had already given that person the object, or that he had not given it to him.
For things that have no physical substance, where there is no object involved but only an action:
"she'ishan v'shelo ishan" - that he swore he would sleep in the future, or that he would not sleep.
"sheyashanti v'shelo yashanti" - that he swore he had slept in the past, or that he had not slept.
"she'ezrok tz'ror la'yam v'shelo ezrok" - that he swore he would throw a stone into the sea in the future, or that he would not throw it.
"shezarakti v'shelo zarakti" - that he swore he had thrown a stone into the sea in the past, or that he had not thrown it.
The view of Rabbi Yishmael:
Rabbi Yishmael disagrees with the first tanna and with everything we have seen until now regarding oaths, namely that they comprise four categories including past and present. In his view, "eino chayav ela al he'asid lavo" - a person is liable for an oath of expression only when he swears about what will happen in the future, to do something or not to do it, but not about something that already occurred in the past. His source is the verse "leharah o l'heitiv" - that he will do something negative or that he will do something positive, language that indicates the future and says nothing about the past.
Rabbi Akiva's response:
Rabbi Akiva said to him: if so, if we read the language of the verse that narrowly, "ein li ela devarim she'yesh bahen hara'ah v'hatavah" - then the oath would take effect only upon negative or positive matters. "devarim she'ein bahen hara'ah v'hatavah minayin?" - how would an oath take effect upon a completely neutral action, such as throwing a stone into the sea, which is neither good nor bad?
Rabbi Yishmael answered: I learn this from the inclusive language of the verse, that is, from a wording in the Torah that broadens and includes, even though the matter is not stated explicitly. Rabbi Akiva answered him: if the verse includes neutral matters, then the verse includes past matters as well, and not only future ones.
The Root of the Dispute - The Rules of Derivation:
The Gemara explains that their disagreement rests on a fundamental principle: how to expound three expressions in the Torah - a general statement, followed by a specific detail, followed once again by a general statement:
The View of Rabbi Akiva - Ribbui, Miut, Ribbui (Inclusion, Exclusion, Inclusion): The inclusion is the broadening general term, the exclusion is the narrowing detail, and after it comes a further inclusion. Read this way, the verse included everything and excluded only a single item. "Mi shenishba" - "one who swears" is an inclusion; "lehara o leheitiv" - "to do harm or to do good" is an exclusion; "lechol asher yevatei ha'adam bishvuah" - "regarding anything a person may utter in an oath" is a further inclusion. The result is that everything is included: whether positive or negative, whether about the future or the past, and the only thing excluded is a matter of mitzvah - for a person cannot take an oath not to fulfill a mitzvah.
The View of Rabbi Yishmael - Klal, Prat, U'chlal (General, Specific, General): Working with those very same words, he applies the method of a general statement, a specific detail and a general statement, whose rule is to include only what resembles the detail. Just as the detail here is doing something positive or negative in the future, so too everything that is yet to occur is included - even neutral actions that involve neither harm nor benefit. But the inclusion is limited to matters that will happen in the future alone, and not to matters that already occurred in the past.
In summary: In this Mishnah we learned that an oath takes effect regarding one's own affairs and the affairs of others, regarding matters of substance and matters without substance, and in all of these both regarding the past and regarding the future. Rabbi Yishmael limits liability to the future alone, based on the wording "to do harm or to do good," while Rabbi Akiva includes the past as well. The root of the dispute lies in the rules of derivation: Rabbi Akiva expounds inclusion, exclusion and inclusion, and excludes only a matter of mitzvah; whereas Rabbi Yishmael expounds general, specific and general, and includes only what resembles the detail - namely, whatever pertains to the future.