Your retraction doesn’t work with these four exceptions TB Nedarim 87

On daf Nedarim 87 we learn how quickly a person can change his mind after vowing and the retraction works. If he changes his mind and retracts within the time required for speaking (tokh kedai debur-תּוֹךְ כְּדֵי דִבּוּר) a short phrase is like that of continuous speech. If a person changes his mind before someone could say “Shalom rabbee umoree (שלום רבי ומורי), Shalom my rabbi and teacher,” then his retraction takes effect. However, if it is longer than that short phrase (akhar kedai debur- אַחַר כְּדֵי דִיבּוּר), then his retraction is null and void.

“And the halakha is: The legal status of a pause or retraction within the time required for speaking (tokh kedai debur-תּוֹךְ כְּדֵי דִבּוּר) a short phrase is like that of continuous speech, and so a person can retract what he first said if he issues the retraction within this period of time after he finished speaking.” (Sefaria.org translation)

There are four exceptions to this principle of tokh kedai debur-תּוֹךְ כְּדֵי דִבּוּר. “This principle holds true in almost every area of halakha, except for the case of one who blasphemes God; or in the case of an idol worshipper, who verbally accepts an idol as his god; or one who betroths a woman; or one who divorces his wife. In these four cases, a person cannot undo his action, even if he immediately retracts what he said within the time required for saying a short phrase.” (Sefaria.org translation)

The Ran explains the psychology behind this principle of tokh kedai debur-תּוֹךְ כְּדֵי דִבּוּר. Tokh kedai debur-תּוֹךְ כְּדֵי דִבּוּר works because we are in constant editing mode when speaking. If something doesn’t come out exactly right, we correct it immediately. For example, when I say something incorrectly I merely say “scratch that” and correct my mistake.

There are some things that a person never says spontaneously, but thinks the matter through. That’s why there are these four exceptions, the blasphemer, the idol worshiper, the person who betroths a woman, and a person who divorces his wife. In these four cases, a person doesn’t do any of these acts on the spur of the moment. Who proposes to a woman without forethought?! Because there is forethought the principal tokh kedai debur-תּוֹךְ כְּדֵי דִבּוּר doesn’t work.

What is the genesis of this principle? Rebbeinu Tam teaches that the principal of tokh kedai debur-תּוֹךְ כְּדֵי דִבּוּר was instituted by the rabbis. When a student was in the midst of negotiating a sale and his rebbe walks by, he can’t ignore is him. He has to acknowledge him and say hello, “Shalom rabbee umoree (שלום רבי ומורי -Shalom my rabbi and teacher.” If a person changes his mind before someone could say “Shalom rabbee umoree (שלום רבי ומורי -Shalom my rabbi and teacher”), he can immediately retract what he was bargaining about.