אם יש בו מום יעלה וישחוט ואם לאו לא ישחוט ר' שמעון אומר כל שאין מומו ניכר מבעוד יום אין זה מן המוכן:
If it has a permanent blemish, owing to which it may be slaughtered and eaten, he may raise it from the cistern and slaughter it; but if it does not have a blemish, or if its blemish is temporary, he may not slaughter it. Rabbi Shimon says: Even if it has a blemish, it is prohibited to slaughter it, as any firstborn animal whose blemish is not perceptible while it is still day, i.e., on the day before the Festival, is not considered to be among the animals prepared prior to the Festival for use on the Festival.
גמ׳ במאי קא מפלגי אי נימא ברואין מומין קמפלגי דר' יהודה סבר רואין מומין בי"ט ור' שמעון סבר אין רואין מומין בי"ט ולפלגו ברואין מומין דעלמא
GEMARA: The Gemara asks: With regard to what principle do Rabbi Yehuda and Rabbi Shimon disagree? If we say that they disagree about whether or not one may examine blemishes on a Festival, such that Rabbi Yehuda holds that one may examine blemishes on a Festival, and Rabbi Shimon holds that one may not examine blemishes on a Festival, if so, let them disagree with regard to examining blemishes in general on a Festival and not only with respect to the particular case of a firstborn that fell into a cistern.
בכור שנפל לבור אצטריכא ליה סד"א משום צער בעלי חיים לערים ולסקיה כר' יהושע קמ"ל
The Gemara answers: It was necessary to teach the disagreement with regard to the case of a firstborn that fell into a cistern, as it could enter your mind to say that because of the matter of the suffering of living creatures, one should employ an artifice to circumvent the halakha and raise the animal from the cistern. This would be in accordance with the opinion of Rabbi Yehoshua, who states elsewhere (37a) with regard to a different case that one may employ an artifice in order to rescue an animal that fell into a cistern on a Festival. Therefore, the mishna teaches us that Rabbi Yehuda and Rabbi Shimon disagree even in the case of a firstborn that fell into a cistern.
אי הכי לא ישחוט לא יעלה וישחוט מבעי ליה לא צריכא דעבר ואסקיה סד"א לשחטיה קמ"ל
The Gemara asks: If so, if the mishna mentions the case of a firstborn that fell into a cistern in order to teach that an artifice may not be employed to raise the animal from the cistern, the phrase: He may not slaughter it, is inaccurate. Rather, it should have stated: He may not raise the animal and slaughter it. The Gemara answers: No, this teaching is necessary in a case where he transgressed the prohibition and already raised it, as it could enter your mind to say that he may now slaughter it. Therefore, the mishna teaches us that even then he may not do so.
לשחטיה הא תם הוא לא צריכא דנפל ביה מומא והא מוקצה הוא
The Gemara expresses wonder at this answer: How could one think that he may now slaughter it? Isn’t the animal unblemished? How could one imagine that it is permitted to slaughter a firstborn that is unblemished? The Gemara answers: This teaching is necessary only in a case where it developed a blemish after it fell. The Gemara challenges this argument: But how could one think that he may now slaughter the animal? Doesn’t it fall into the category of muktze, as it was not fit to be eaten on the eve of the Festival, since at that time it was still unblemished? In that case, it should remain in the category of muktze for the duration of the Festival.
אלא דנפל ביה מום עובר מערב יום טוב והשתא הוה ליה מום קבוע מהו דתימא דדעתיה עלויה ונשחטיה קמ"ל:
Rather, the mishna is speaking of a case where the animal developed a temporary blemish, one that might eventually heal, on the eve of the Festival, and now, after falling, it has a permanent blemish. Lest you say that his mind was set on the animal as food already before the Festival due to the temporary blemish and therefore he should now be allowed to slaughter it, the mishna teaches us that since it was not fit to be eaten before the Festival, it is not considered prepared for use on the Festival. Rather, it falls into the category of muktze and may not be slaughtered.
ת"ר בכור תם שנפל לבור ר' יהודה הנשיא אומר ירד מומחה ויראה אם יש בו מום יעלה וישחוט ואם לאו לא ישחוט אמר לו ר' שמעון בן מנסיא הרי אמרו אין רואין מומין ביום טוב כיצד נולד בו מום מערב "ט אין מבקרין אותו בי"ט נולד בו מום
The Sages taught the following baraita: With regard to an unblemished firstborn that fell into a cistern on a Festival, Rabbi Yehuda HaNasi says: An expert in these matters goes down into the cistern and examines the animal. If it now has a permanent blemish as a result of the fall, he may raise it from the cistern and slaughter it; but if not, then even if he proceeds to raise it, he may not slaughter it, even if afterwards it develops a blemish. Rabbi Shimon ben Menasya said to him: The Sages of earlier generations already said that one may not examine blemishes on a Festival. How so? If a blemish came into being on the eve of a Festival, one may not examine it on the Festival itself to see whether it is in fact of the type that permits the animal to be slaughtered. And if the blemish came into being