QUESTION: The Gemara (end of 72b) suggests that when Rava says that Edim Zomemim become invalid witnesses "from now on" ("mi'Kan ul'Haba"), he actually agrees with Abaye that mid'Oraisa they become invalidated l'Mafrei'a, from the time that they gave false testimony. The reason why the Rabanan upheld any testimony which they gave between that time and the time that they were found to be lying is in order to protect any buyers who purchased land and signed these witnesses on their contracts ("Mishum Peseida d'Lekuchos").

Why were the Rabanan not also concerned about protecting the sellers from loss? The seller claims that the sale never took place and that the witnesses signed on the contract are invalid and their testimony is not acceptable. Why were the Rabanan more interested in protecting the buyers than the sellers?

ANSWER: The CHIDUSHEI HA'RAN in Sanhedrin (27a, DH Rava) answers that there is no concern that the sellers will lose out because the buyer is in possession of the land and has a bill of sale which states that the seller sold it to him. Since he has both possession of the land and a bill of sale, it is clear that the seller sold it to him, for if he did not sell it to him, why did the seller not take him to court earlier when he saw this person occupying his land? The only concern is that the contract itself is not a valid contract since the witnesses that signed it are invalid, and the buyer is left without proper proof of the sale. Therefore, the Rabanan said that such witnesses are acceptable when signed on a contract in order to maintain order in the marketplace.

OPINIONS: The Gemara discusses the concept of "Toch Kedei Dibur k'Dibur Dami." As the Gemara explains, "Toch Kedei Dibur" is the length of time that it takes a student to greet his teacher ("Shalom Alecha Rebbi"). Within this small amount of time after a person's act or speech, the act or speech is not considered finished but rather still continuing ("k'Dibur Dami"). Consequently, although the person has physically stopped performing the act or stopped speaking, within this amount of time he may act or say something that will abrogate his previous actions or words (or, in the case of the Gemara here, he may add something to his previous words which will be considered to have been said at the same time as his previous words).

What is the source for the principle of "Toch Kedei Dibur k'Dibur Dami," and what is the source for the exceptions? The Rishonim differ with regard to the source and with regard to the way in which "Toch Kedei Dibur" functions.

(a) The RAN in Nedarim (87a) writes that the principle of "Toch Kedei Dibur" and its exceptions are mid'Oraisa. The Torah assumes that a person is never totally committed to his speech or actions and he always reserves the right to retract within the small amount of time of "Toch Kedei Dibur." However, when he performs actions which are of a very severe nature (the exceptions mentioned in the Gemara in Nedarim, such as blasphemy (Megadef), idolatry (Avodah Zarah), marriage, and divorce), he 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 retract.

The RITVA in Nedarim adds that "Toch Kedei Dibur" is "k'Dibur Dami" because within that amount of time a person's lips are stilled involved in the speech he just articulated, and he is considered as though he is still speaking.

(b) TOSFOS here (DH Ki Leis Lei) quotes RABEINU TAM who explains 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 or his friend while in the midst of a purchase, or to enable a witness to greet his teacher or his friend while in the midst of giving testimony (since the Gemara in Berachos (6b) says that one who is greeted by someone else and does not return the greeting is called a "Gazlan"), in such a way that greeting does not constitute an interruption between the words he said before and the words he said afterwards. Tosfos asks, however, that "Toch Kedei Dibur" cannot be a Takanah d'Rabanan because it applies even with regard to Halachos that are mid'Oraisa.

(c) The RASHBAM in Bava Basra (129b) writes that the principle of "Toch Kedei Dibur" is mid'Oraisa in all cases, including the exceptions mentioned in the Gemara in Nedarim. Mid'Oraisa, one may retract within Toch Kedei Dibur even in cases of Megadef, Avodah Zarah, marriage, and divorce. However, the Rabanan enacted that "Toch Kedei Dibur" does not work in those cases. They enacted that it does not work in cases of Megadef and Avodah Zarah because of the severity of the act. They enacted that it does 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.

These explanations of "Toch Kedei Dibur," however, do not seem consistent with the Gemara here. The Gemara explains that according to Rebbi Yosi, when the witnesses (who testified about the Geneivah and the Tevichah) are found to be lying about the Tevichah (they are found to be Edim Zomemim), their testimony about the Geneivah is also invalidated. It makes sense that, retroactively, all of their testimonies that they gave after the moment that they testified falsely about the Tevichah are invalidated. Why, though, is the testimony that they gave (i.e. about the Geneivah) before the Tevichah invalidated? Just because it was within "Toch Kedei Dibur" of their testimony about the Tevichah is not a reason to invalidate it!

The AMUDEI OR suggests that since the principle of "Toch Kedei Dibur" enables the witnesses to retract their testimony (about the Geneivah) within the time of "Toch Kedei Dibur," their entire testimony is viewed as though it takes effect only after "Toch Kedei Dibur" has passed from the time they stopped testifying. It is at that point -- when they no longer can retract what they said -- that they show that their intentions are absolute and irrevocable, and thus it is at that point that their testimony takes effect and becomes binding and official. Therefore, when they are proven to be Edim Zomemim with regard to their testimony about the Tevichah, their testimony about the Geneivah is also invalidated since both parts of their testimony are considered to have been said at the same time -- the moment that "Toch Kedei Dibur" passed and they could no longer retract any of their testimony. (I. Alsheich) (See Insights to Nedarim 87:1 and Bava Basra 129:2.)

QUESTION: The Gemara says that the amount of time of "Toch Kedei Dibur" refers to the amount of time that it takes a Talmid to give a greeting to his teacher.

How can this be the time of "Toch Kedei Dibur" if a Talmid is prohibited from initiating a greeting to his teacher, as the Gemara in Berachos (27b) says, "One who gives a greeting (of 'Shalom') to his teacher causes the Shechinah to be removed from the world"? (TOSFOS)

(a) TOSFOS here and in Berachos answers that the Gemara in Berachos refers to a Talmid who greets his teacher in the same manner in which he greets his friend ("Shalom Aleicha"). The Gemara here refers to a greeting of respect for his teacher ("Shalom Aleicha Rebbi"), which is permissible. This is also the explanation of RASHI in Berachos (DH Shalom l'Rabo).

(b) TOSFOS in Berachos answers further that perhaps the Gemara here in Bava Kama refers to a Talmid Chaver (a colleague) and not to a full-fledged Talmid. A Talmid Chaver is permitted to greet his teacher who is also his colleague. (It is clear from Tosfos that even a Talmid Chaver must greet his teacher with a greeting of respect, as the Gemara says, "Shalom Aleicha Rebbi u'Mori." This implies that an ordinary Talmid may not greet his teacher altogether, even with a greeting that expresses respect. This is indeed the ruling of the Yerushalmi as mentioned by the REMA in Yoreh De'ah 242:16.)

(c) Although our text of the Gemara in Berachos says that a Talmid may neither greet his teacher (i.e. initiate the greeting) nor return a greeting to his teacher, the RIF, ROSH, and TALMIDEI RABEINU YONAH in Berachos do not have the Girsa that a Talmid may not return a greeting. Accordingly, they explain that when the Gemara here says that "Toch Kedei Dibur" is the time it takes a Talmid to greet his teacher, it refers to the time it takes for him to return a greeting which, according to their Girsa, is permissible.