LIABILITY FOR SLAUGHTERING AN INVALID PESACH (Yerushalmi Halachah 5 Daf 43a)
משנה הפסח ששחטו שלא לשמו בשבת חייב עליו חטאת
(Mishnah): If one slaughtered a Korban Pesach Lo Lishmah on Shabbos, he is liable a sin-offering.
ושאר כל הזבחים ששחטן לשם הפסח אם אינן ראויין חייב אם ראויין ר' אליעזר מחייב חטאת ר' יהושע פוטר
All other sacrifices that were slaughtered as a Pesach -
If they are not suitable, he is liable.
If they are suitable, R' Eliezer says that he is liable and R' Yehoshua says that he is exempt.
א''ר אליעזר מה אם הפסח שהוא מותר לשמו כששינה את שמו חייב זבחים שהן אסורין לשמן כששינה את שמן אינו דין שיהא חייב
R' Eliezer: If for the Pesach, that may be slaughtered on Shabbos Lishmah, when he intended it for another sacrifice, he is liable; for sacrifices that may not even be slaughtered Lishmah on Shabbos, if he intended them for another sacrifice, he will surely be liable!
אמר לו ר' יהושע לא אם אמרת בפסח ששינה את שמו בדבר אסור תאמר בזבחי' ששינן בדבר מותר
R' Yehoshua responds: No - if you say it about a Pesach that was changed to a sacrifice that may not be slaughtered on Shabbos; would you say it about sacrifices that were changed to a sacrifice that may be slaughtered on Shabbos?!
א''ל ר' אליעזר אימורי ציבור יוכיחו שהן מותרין לשמן והשוחט לשמן חייב
R' Eliezer responds: Public sacrifices prove it, as they are permitted Lishmah and one who slaughters other sacrifices for them is liable!
א''ל ר''י לא אם אמרת באימורי ציבור שיש להן קיצבה תאמר בפסח שאין לו קיצבה
R' Yehoshua: No - if you say it about public sacrifices that are limited (for example, it is known that the Tamid offering is only offered once in the morning, so if he acts incorrectly, it will be considered Shogeg - an act involving negligence - rather than a mere mistake. However, the Pesach does not have such a limit as many are brought, so he could make a mistake.
ר''מ אומר אף השוחט לשם אימורי ציבור פטור
R' Meir: Even one who slaughters other sacrifices as public sacrifices (on any Shabbos) is exempt.
גמרא מתניתא ביודע בו שהוא פסח ושחטו לשם שלמים
(Gemara): The Mishnah refers to when he knows that it is a Pesach offering and he slaughtered it as a Shelamim offering.
היה יודע בו שהוא שלמים ושחטו לשם עולה [דף נ עמוד א (עוז והדר)] רבי מנא אמר יש בעשייתו מצוה רבי יוסה אמר אין בעשייתו מצוה
If he knows that it is a Shelamim and he slaughters it as an Olah -
R' Mana said that its performance is a Mitzvah and it is valid.
R' Yosa said that its performance is not a Mitzvah and it is invalid.
אילי ציבור שהיה סבור שהן כבשים ושחטן לשם אילים שמא לא עלו לציבור לשם אילים
Question: The two public rams (that are brought as an Olah on Shavu'os), that he thought were sheep (to be used for the Shelamim) and he slaughtered them as rams - would they not fulfil the requirement of the public to bring rams?
[דף מג עמוד ב] ותני כן אילי ציבור שהיה סבור שהן כבשים ושחטן לשם אילים כבר עלו לציבור לשם חובה
Support (Beraisa): Public rams that he thought were sheep and he slaughtered them as rams, the public have fulfilled their obligation.
מתניתא בסבור בו שהוא פסח ושחטו לשם פסח
The Mishnah (that taught that all other sacrifices that were slaughtered as a Pesach, if they are not suitable, he is liable) referred to when he thought it was a Pesach and he slaughtered it as a Pesach.
היה יודע בו שהוא שלמים אלא שהיה סבור לומר שמותר לשנות שלמים לשם פסח רבי מנא אמר אין בעשייתו מצוה רבי יוסה אמר יש בעשייתו מצוה
If he knew it was a Shelamim but he thought that it is permitted to change a Shelamim into a Pesach -
R' Mana said that its performance is not a Mitzvah and it is invalid.
R' Yosa said that its performance is a Mitzvah and it is valid.
מסתברא דר' מנא בקדמייתא ודרבי יוסה באחרייתא
It is logical to say that the Halacha follows R' Mana in the former case (i) and it follows R' Yosa in the latter case (m).
אמרין לית הדא דרבי ליעזר תתובה על דרבי יהושע דו יכיל מימיר ליה האיך את משיביני מדבר שדרכו לחלף על דבר שאין דרכו ליתחלף
The Kal VeChomer of R' Eliezer (see earlier (c)) is not a successful proof against R' Yehoshua as he could respond that for sacrifices that were changed to become a Pesach, it is logical to say that he is exempt since it is normal to change them on the 14th. However, it is abnormal to change a Pesach into another sacrifice on the 14th.
ולא הדא דרבי יושוע תתובה על דרבי אליעזר דו יכיל מימיר ליה הרי פסחו של ראובן ששחטו לשם שמעון הרי שינהו לדבר כשר ותימר חייב
Similarly, the response of R' Yehoshua to the Kal Vechomer of R' Eliezer (see earlier (d)) is not valid, as R' Eliezer could say suggest a different Kal Vechomer - If the Pesach of Reuven which was slaughtered for Shimon was changed into something valid and he is nevertheless liable; for sacrifices that are prohibited to slaughter Lishmah, he will certainly be liable.
רבי מאיר אומר השוחט לשם אימורי צבור פטור
The Mishnah had taught: R' Meir says - even one who slaughters other sacrifices as public sacrifices (on any Shabbos) is exempt.
א''ר לעזר דברי רבי מאיר אפילו עגל
R' Elazar: R' Meir held that if one slaughtered a calf of Shelamim as a public sacrifice, he is liable.
את שמע מינה תרתיי. [דף נ עמוד ב (עוז והדר)] את שמע מינה דבר שאין לו קיצבה ודבר שאין דרכו להתחליף ויש בעשייתו מצוה
One can learn two things from this statement of R' Elazar -
Public sacrifices are not limited (see earlier (f)).
It is not normal to change their identity (see earlier (o)).
However, their performance is a Mitzvah and they are valid (even though the owner has not fulfilled his obligation).
THE CONCEPT OF "ITS PERFORMANCE IS A MITZVAH'' (Yerushalmi Halachah 5 Daf 44a)
[דף מד עמוד א] ר''ש בן לקיש אמר יש בעשייתו מצוה כגון יבמתו נדה ובא עליה
R' Shimon ben Lakish: An example of "its performance is a Mitzvah'' is performing Yibum (Levirate marriage) with a lady who is a Niddah. (Yibum is performed by having marital relations, which in this case is prohibited since she is a Niddah. In this case, even R' Meir agrees that he is liable as he should have verified in advance whether or not she was a Niddah.)
ר' יוחנן אמר אין בעשייתו מצוה כגון שני שפודין אחד של שחוטה ואחד של נבילה וביקש לוכל מזה ואכל מזה
R' Yochanan: An example of "its performance is not a Mitzvah'' is when there are two spits, one with slaughtered meat (of Kodshim) and one with meat that was not slaughtered - he wished to eat the slaughtered and he ate the non-slaughtered. (In this case, R' Meir agrees that he is exempt.)
מתניתא פליגא על רבי יוחנן (שבת) [שכח] ומל את שלאחר שבת בשבת רבי אליעזר מחייב חטאת ורבי יהושע פוטר
Question against R' Yochanan (Mishnah): (If there were two babies, one was scheduled to have his circumcision on Shabbos and the other was to have it on Sunday.) If he forgot and on Shabbos he circumcised the baby who was scheduled to have it done on Sunday -
R' Eliezer says that he is liable (a sin-offering).
R' Yehoshua says that he is exempt.
הרי אין בעשייתו מצוה ור' יהושע פוטר
Conclusion of question: For this baby, the performance of his circumcision was not a Mitzvah and R' Yehoshua says that he is exempt?
שמואל קפודקי' אמר למחר יש בעשייתה מצוה
Answer (Shmuel Kepudkiya): Tomorrow however, the circumcision will be a Mitzvah (so it is considered that his mind was busy with performing a Mitzvah).