"and slaughter the Pesach (Passover): It is a mitzvah to slaughter it as a Pesach offering. If he does not offer it as such, he transgresses the mitzvah. I might think that in the above instance) it is, nevertheless kasher. It is, therefore, written (Ibid. 27) "It is a Paschal sacrifice to the L–rd." Scripture repeats it to render it unfit (in the above instance.) From here it was ruled: All sacrifices which were slaughtered not "as such" are kasher, but they are not accounted to the owners as the fulfillment of an obligation—except for the Pesach and the sin-offering, (which are not kasher.)