The Knife

The Gemorah (Zevachim 97b) derives from the verse (22:10) "Avrohom took the knife," that a keli as opposed to the harp edge of a reed is required to do the shechita of kodshim.  Rashi Zevachim (98a) understands that this means that the shechita must be done with a kli shares.  This would seem to run at odds with Rashi Menachos (82b) that explains the chiddush of the Gemorah is that an act of shechita is requires on a korban and its not enough to do melika.  According to Rashi Menachos the rule is just coming to tell us you need shechita but you don't see the need for a kli shares.  The Rishonim  (Tosfos Zevachim 47a and Rishonim Chullin 3a) debate this point if the halacha says that a keli is required or its not enough with any keli but a kli shares is required.  The Achronim ask how do we see in the verse that it was a kli shares?  Furthermore, the Rambam (Maaseh Karbonos 4:7) rules that the requirement is to use  kli shares but ex post facto any shechita is good (even without a keli.)  Why is the law only lichatchila?

The question seems to be is this law of a keli required for the shechita of kodshim is that a rule in shechita which is only said in regard to kodshim or is it in a rule in kodshim.  The Rishonim that understand that a keli sharas is required is because they understand if the law says a keli is required it must be a law in kodshim.  If its a law in kodshim than it has the laws of kelim d'hekdash and requires a kli sharash.  It's not some extrapolation from the verse that tells us the requirement of kli sharash, its part of the requirement of keli.  This is the opinion of the Rambam as well.  Therefore, he follows the general rule that by kodshim laws are binding even ex post facto only if there are two verses telling us the law.  Here, there aren't two verses, therefore the rule isn't binding b'deavad.  The Rishonim that don't require a kli sharash just any keli, hold that the law is telling us a law in slaughtering.  It happens to be that this rule of slaughtering only applies to animals of kodshim only, tbut we can't extrapolate from there any requirement of kli sharash (Dibros Moshe Chullin daf 12.)

The Ritvah (Chullin 3a) says that a kli sharas is necessary to be mekadash the blood of the korban (as the Gemorah says in Sotah 14b) but its not a kli sharash gamur and therefore there is no pesul of yotzeh, of the blood leaving the mikdash.  What does he mean, what is a kli sharash gamur or not gamur?  Rav Dovid Elon (Masseh Yad volume 2) explains that we find two types of kli sharash.  We find kli sharash that cause kedusha to other things like the kalim used to receive blood of a korban or put minachos in.  We find a second kind of kli sharash, that which is kodesh in its own right, but doesn't make other things kodesh such as the menorah and aron.  The Ritvah means that the shechita knife has to be kodesh but it isn't mekadesh the blood (see also Tosfos Rosh in Sotah.)  The problem is that this seems to be the opposite of what the Ritvah is saying.  The Ritvah says that the knife is a kli sharash in regard to give kedusha to the blood, clearly he is saying it is a kli sharash to be mekadesh the blood?