The witnesses do not become zomemim unless they discredit them personally. How so? [If] they said, “We testify against so-and-so that he killed someone”; [and others] said to them, “How can you testify [so], when this murder victim,” or “this murderer,” “was with us on that day in such and such a place” —- these are not [considered] zomemim. But [if] they said to them, “How can you testify [so], when you were with us on that day in such and such a place,” these are [considered] zomemim, and they are executed by their testimony.

[If] others came and they discredited them, [and still] others came, and they discredited them [too], even one hundred, all of them are executed. R' Yehudah says: This is a group of plotters, and only the first group is executed.

Zomemim witnesses are not executed unless the verdict has been delivered. For the Sadducees say: Unless he had been exe-cuted, as it is said: A life for a life. The Sages said to them: Has it not already stated (Deut. 19:21): And you shall do to him as he planned to do to his brother —- indicating that his brother is still alive! If so, why does it say, A life for a life? Because it might be thought that from the time their testimony is ac-cepted, they may be executed; [the Torah] therefore states: A life for a life —- [to teach] that they are not executed unless a verdict has been issued.

. By the testimony of two witnesses or three witnesses shall the one who is to die be put to death (Deut. 17:6). Now if the tes-timony may be established by two, why did Scripture specify by three? It is to compare three to two: Just as three can discredit two, so two can discredit three. How do we know that [this is true] even [for] one hundred? To teach [this] it states: witnesses. R' Shimon says: Just as two are not executed unless both are proved zomemim, so three are not executed unless the three of them are proved zomemim. How do we know that [this is true] even [for] one hundred? To teach [this] it states: witnesses. R' Akiva says: The third witness is mentioned only for the purpose of dealing stringently with him and to make his sen-tence the same as these. Now if Scripture punished one who joined transgressors like the transgressors [themselves], how much more will it reward the one who joins those who perform a mitzvah the same as those who perform the mitzvah!