The Gemoro discusses Toch KeDei Dibbur regarding Haforas Hedorim
(where the husband was Mefer to the wrong person and found out his mistake),
and Keriah (where the person tore Keriah for the wrong person).
1) Doesn't Toch KeDei Dibbur normally relate to speech, i.e. one said something, then regretted it, and said something else instead (e.g. if forgot HaMelech HaKodosh). Here we are applying it to actions (Keriah).
2) Furthermore, we are saying that the action can be undone/changed by a decision made later (maybe we say that the action carries on for this time?)
WITHOUT another action; in the usual cases we just say that his first speech is not considered, and his second speech counts.
- a question: if a person said Mashiv HoRuach UMorid HaGoshem in summer, and regretted it within Toch KeDei Dibbur, I think he has to go back to Ata Gibor, i.e. we don't say he can "undo" his speech with subsequent regret.
1) "Toch Kedei Dibur" does not necessarily relate to speech. See what we wrote in the Insights (below) regarding the source for the principle of "Toch Kedei Dibur:"
[From Insights to Nedarim 87]:
OPINIONS: The Gemara mentions that the principle of "Toch Kedei Dibur k'Dibur Dami" applies for all Halachos except for blaspheming (Megadef), idolatry (Avodah Zarah), marriage, and divorce.
The Rishonim differ regarding the source for this principle and regarding the mechanics of how it works.
(a) The RAN writes that both the principle of "Toch Kedei Dibur" and its exceptions are mid'Oraisa . The logic behind this is that a person is never totally committed to his actions and reserves the right to renege within the small amount of time of Toch Kedei Dibur. However, when performing actions which are of such a severe nature (the exceptions mentioned in the Gemara), a person does not begin the action until he is absolutely committed to doing it, and therefore he does not reserve in his mind the right to renege.
(b) The Ran writes in the name of the Ramban in Bava Basra, who quotes RABEINU TAM, that the Halachah of "Toch Kedei Dibur" is a Takanah d'Rabanan. The Rabanan instituted this principle in order to enable a buyer to greet his teacher while in the middle of a purchase, without that greeting acting as an interruption between the words he was saying beforehand and the words he says afterwards. TOSFOS cites this opinion in the name of Rabeinu Eliezer. Tosfos asks, however, that it "Toch Kedei Dibur" cannot be a Takanah d'Rabanan, because it is said even with regard to Halachos that are mid'Oraisa.
(c) The RASHBAM (Bava Basra 129b) writes that the principle of "Toch Kedei Dibur" is mid'Oraisa in all cases, including those exceptions mentioned in the Gemara (that is, one can rescind within "Toch Kedei Dibur" even in cases of Megadef, Avodah Zarah, marriage, and divorce), but the Rabanan enacted that it does not work in those cases. They enacted that it not work in cases of Megadef and Avodah Zarah because of the severity of the act, and that it not work in cases of marriage and divorce in order to prevent rumors from spreading which would ruin the reputation of the children born from the union.
QUESTION: According to the opinions of the Ran and Rabeinu Tam, the cases of the application of "Toch Kedei Dibur" mentioned in our Sugya are problematic. The Gemara says that if one tore Keri'ah for a relative before the relative died, and then the relative died within "Toch Kedei Dibur" of the Keri'ah, the mourner need not tear again. The reasoning of the Ran certainly does not apply, for the person who tore Keri'ah was not transacting any sort of deal from which he might wish to renege. Rather, at the time he tore Keri'ah, he was not yet obligated to tear, because the relative had not yet died, and thus his Keri'ah should be ineffective! The same is true of the case where a man annulled a Neder mistakenly thinking that it was his wife who made the Neder, and "Toch Kedei Dibur" he discovered that it was actually his daughter who made the Neder. The Gemara applies the principle of "Toch Kedei Dibur" even though there is no question of indecision, but merely a lack of knowledge which was only rectified after the act.
According to Rabeinu Tam, who explains that the principle of "Toch Kedei Dibur" is a Takanah d'Rabanan in case one needs to greet his teacher in the middle of a transaction, the case of Keri'ah is similarly problematic, since there is no reason to apply the principle of "Toch Kedei Dibur" there.
ANSWER: TOSFOS in Bava Kama (73b) answers that even though Rabeinu Tam's reasoning for "Toch Kedei Dibur" does not apply to Keri'ah, nevertheless the Rabanan instituted the leniency of "Toch Kedei Dibur" as a special leniency in the Halachah of Keri'ah. TOSFOS in Bava Basra (129b) answers that "Toch Kedei Dibur" applies to Keri'ah because the Rabanan instituted a "Lo Plug" -- since in some situations the rule applies, they enacted that it should apply in all situations.
These answers, though, do not answer the questions on the Ran's opinion, and we remain with the questions from the Halachos of Keri'ah and Hafarah. It must be that, according to the Ran, the basic principle of "Toch Kedei Dibur k'Dibur Dami" is a universal rule that anything which happens within the time frame of "Toch Kedei Dibur" is non-sequential; it is immaterial what happened first. Therefore, we can consider the Keri'ah as if it happened after the death. The Ran said his reasoning only in order to differentiate between normal acts and transactions to which the principle of "Toch Kedei Dibur" applies, and Avodah Zarah (and Megadef), Gitin and Kidushin -- acts which are final and irrevocable once performed, due to their severity, and are therefore excluded from the rule of "Toch Kedei Dibur k'Dibur Dami."
2) As for your point about Mashiv ha'Ru'ach u'Morid ha'Geshem, the reason that one must return is because there was nothing actually accomplished, such as a transaction, from which regret alone will suffice. It is for that reason that the only way to rectify the situation is to return and delete it. However, when a Dibur has accomplished a Chalos, it is sufficient to regret the outcome.