The gemara brings a braissa which says Tana Beribi Omer Lo Hargu Neheragin, Hargu Ein Neheragin and the gemara asks on this that we should say a kal vachomer that of already by Lo Hargu Neheragin then Kol She'Kein we should say Im Hargu Neheragin?
My question is that the Mishna just told usthat we learn from va'Asisem Lo Ka'asher Zamam La'asos l'Achiv that only if the Achiv is still alive do we say Ka'asher Zamam but not if he is dead so if so how could the gemara ask let's say a Kal v'Chomer to tell us that even if he is dead we should kill the witnesses? (I'm not sure if the Pnei Yehoshua asks this question but I'm not really sure what he is answering)
Many thanks
Benzi
Benzi, London
First, I wiil try, bs'd, to explain the Pnei Yehoshua.
1) The Pnei Yehoshua writes that there appears to be a dispute between the Mishnah and Beribi, mentioned in the Beraisa in the Gemara, and the father of Beribi, also mentioned in the same Beraisa. The Mishnah learns from the verse "l'Achiv" that we do to the Edim Zomemim only what they wanted to do to their victims if the "brother" is still alive, but if "Hargu, Ein Neheragin." The two Tana'im (namely, Beribi and his father) mentioned in the Beraisa both disagree with the Mishnah. Beribi says that if the Edim Zomemim have not yet killed, then they are killed, but if they have already killed, they do not get killed.
2) The Pnei Yehoshua does not say how Beribi knows this Din. However, it is not from the verse "l'Achiv." It seems to me that the Pnei Yehoshua knows that Beribi did not learn it from "l'Achiv" because of your question, Benzi, that if he would have learned it from "l'Achiv" then his father would not have questioned him that it should be a Kal va'Chomer, because a Kal va'Chomer could not push aside an explicit verse.
3) The second answer of the Pnei Yehoshua, on the question of how a Kal va'Chomer can push aside a verse, is to say that the Tana of the Mishnah does not really agree with the Limud from "l'Achiv." The Tana of the Mishnah said this Limud only in an attempt to refute the Tzedukim. If the Tana of the Mishnah does not really agree with this Limud, then there is no reason why a Kal va'Chomer cannot override it.
Kol Tuv,
Dovid Bloom