Pesachim 72A

גמ׳ במאי עסקינן? אילימא בטועה ⁠— שמעת מינה עקירה בטעות הויא עקירה. אלא בעוקר.

Talmud: When the Mishnah speaks of one who slaughtered a Paschal lamb on Shabbat for a different purpose, with what precisely are we dealing? If you say we are dealing with one who erred in that he actually thought this was a different offering and not a Paschal offering, learn from it, i.e., from the fact that the offering is disqualified and he is therefore liable to bring a sin-offering, that the erroneous uprooting of the status of an offering constitutes uprooting, even though he had no intention to do so. It would, however, be surprising to find the Mishnah taking a stand on this issue, as we find elsewhere that it is the subject of an amoraic dispute (Tosafot). Rather, the Mishnah must certainly be referring to one who intentionally uprooted the animal’s designation as a Paschal lamb and offered it as a different offering.

אימא סיפא: ושאר כל הזבחים ששחטן לשום הפסח, אם אינן ראויין ⁠— חייב, אם ראויין הן ⁠— רבי אליעזר מחייב חטאת, ורבי יהושע פוטר. ואי בעוקר, מה לי ראויין, מה לי שאינן ראויין?

If so, say the latter clause of the Mishnah: As for all other offerings that one unwittingly slaughtered on Shabbat for the purpose of a Paschal offering, if they were not fit for the Paschal offering, he is liable to bring a sin-offering. And if they are fit, R' Eliezer deems him liable to bring a sin-offering, whereas R' Yehoshua exempts him. Now if the Mishnah is referring to one who intentionally uprooted the original designation of the animal, which he knew was not a Paschal offering, what does it matter to me whether the animal was fit or unfit? He certainly does not think that he is performing a mitzva; why then does R' Yehoshua exempt him from bringing a sin-offering?