והא מדקתני סיפא ואם שחטו אין מכסין את דמו מכלל (דרישא) בדאית ליה עסקינן
The Gemara challenges this: From the fact that the latter clause teaches: And if he slaughtered it one may not cover its blood, it may be inferred that in the first clause we are dealing with a situation where he does have something with which to cover the blood. If he does not have anything he can use, why is it necessary to state that one may not cover it? And consequently, if he does in fact have material with which to cover the blood, why may he not do so, either with his basket of earth, in accordance with the opinion of Rabbi Yehuda, or with the ashes of a stove?
אלא אמר רבה אפר כירה מוכן לודאי ואין מוכן לספק
Rather, Rabba said that the ashes of a stove, which the mishna stated are prepared, are prepared only for covering the blood in a case of a definite obligation, but they are not considered prepared for a case of uncertainty. Although his intention was to use these ashes to cover the blood of any animal he slaughters, whether in a definite or an uncertain case, they are nevertheless not considered prepared for an uncertain case.
לספק מאי טעמא לא דקא עביד גומא ודאי נמי קא עביד גומא אלא כדר' אבא הכא נמי כדר' אבא
The Gemara inquires: In a case of uncertainty, what is the reason that the ashes are not considered prepared? If the reason is that one makes a hole in the mound of ashes when he removes part of it for covering, in a definite case he also makes a hole. If it is prohibited to make a hole, that prohibition applies in all cases. Rather, one must say, in accordance with the opinion of Rabbi Abba, that the making of this hole is not considered prohibited labor, as he is merely performing a destructive act. If so, here too, in a case of uncertainty, there should be no cause for concern, in accordance with the opinion of Rabbi Abba.
אלא ספק מאי טעמא דלמא עביד כתישה ודאי נמי נגזור משום כתישה ודאי כי קא עביד כתישה אתי עשה ודחי את לא תעשה
Rather, the Gemara retracts from the previous suggestion and offers an alternative: With regard to a case of uncertainty, what is the reason that it is prohibited? The reason is that perhaps one will forget and perform crushing with this earth, to ready it for covering. However, the same problem arises as before: If so, we should also decree against covering the blood in a definite case, because he might crush the earth. The Gemara answers: This presents no difficulty, as when one fulfills the mitzva of covering the blood in a definite case, even if he performs crushing, the positive mitzva of covering the blood comes and overrides the prohibition concerning the desecration of a Festival.
אימר דאמרינן אתי עשה ודחי את לא תעשה כגון מילה בצרעת א"נ סדין בציצית
The Gemara challenges this: Say that we said the following principle: A positive mitzva comes and overrides a prohibition in a case such as the circumcision of a child who has leprosy. Cutting off a leprous blemish is a violation of a prohibition. However, if a baby’s foreskin is leprous, it is permitted to cut it off by circumcision. Alternatively, the principle applies to a case of a linen cloak on which woolen ritual fringes are placed, despite the prohibition against wearing diverse kinds, i.e., a mixture of wool and linen.
דבעידנא דקא מעקר לאו קא מוקים לעשה הכא בעידנא דקא מעקר לאו לא מוקים עשה הא לא קשיא דבהדי דכתיש קא מכסי
The Gemara explains the difference between those halakhot and the issue at hand. In those cases, at the time that one uproots the prohibition, he fulfills the positive mitzva with the same act. However, here, in the case of covering blood, two separate actions are involved, as at the time that one uproots the prohibition, when he crushes the earth, he does not fulfill the positive mitzva of covering the blood. The Gemara answers: This is not difficult, as it is possible to say that when one crushes the earth, he covers the blood with it; he fulfills the positive mitzva by means of the same action through which he uproots the prohibition.
סוף סוף יום טוב עשה ולא תעשה הוא ואין עשה דוחה את לא תעשה ועשה
The Gemara challenges this explanation from a different perspective: Ultimately, a Festival is a mitzva that includes both the positive mitzva of rest and also the prohibition against performing prohibited labor, and there is a principle that a positive mitzva by itself does not override a prohibition and a positive mitzva together.
אלא אמר רבא אפר כירה דעתו לודאי ואין דעתו לספק
Rather, the Gemara rejects the previous explanation, in favor of the following. Rava said: One’s initial intention is to use the ashes of a stove for a mitzva that is definite, and he does not have this intention for cases of uncertainty. One may not use an article on a Festival for a purpose which he did not have in mind beforehand.
ואזדא רבא לטעמיה דאמר רבא הכניס עפר לכסות בו צואה מותר לכסות בו דם צפור דם צפור אסור לכסות בו צואה
The Gemara comments: And Rava follows his regular line of reasoning in this regard, as Rava said: If one brought in earth in order to cover a baby’s excrement with it on a Festival, it is likewise permitted to cover with it the blood of a slaughtered bird. Since he prepared this earth for a case of uncertainty, as it is possible that the baby will not soil the house, he certainly intended to use it for covering the blood of a bird prepared before the Festival for slaughter. If, however, one prepared the earth at the outset to cover the blood of a bird, it is prohibited to cover excrement with it, as he did not know in advance that he would require the earth for this purpose. He had only definite uses in mind, not possible ones such as covering excrement.
נהרבלאי אמרי אפילו הכניס עפר לכסות בו דם צפור מותר לכסות בו צואה
The Sages of Neharbela said: Even if one brought in earth to cover the blood of a bird with it, it is permitted to cover excrement with it, as it cannot be said that he did not intend this usage.
אמרי במערבא פליגי בה ר' יוסי בר חמא ור' זירא ואמרי לה רבא בריה דרב יוסף בר חמא ור' זירא חד אמר כוי הרי הוא כצואה וחד אמר כוי אינו כצואה
They say in the West, Eretz Yisrael, that Rabbi Yosei bar Ḥama and Rabbi Zeira disagree with regard to this issue, and some say it was disputed by Rava, son of Rav Yosef bar Ḥama, commonly mentioned in the Babylonian Talmud as Rava, without the patronymic, and Rabbi Zeira. The Gemara elaborates: One of them said that a koy is similar to excrement in this regard. Just as one may cover the blood of a bird with earth brought in for the purpose of covering excrement, he may likewise use it for covering the blood of a koy, as both the case of excrement and the case of the koy are cases of uncertainty. And the other one said: A koy is not similar to excrement. Since the covering of excrement is common, it is regarded as a definite purpose in comparison to a koy, which is by definition an uncertain case. It is therefore prohibited to cover the blood of a koy with earth prepared for the sake of covering excrement.
תסתיים דרבא הוא דאמר כוי הרי הוא כצואה דאמר רבא הכניס עפר לכסות בו צואה מותר לכסות בו דם צפור דם צפור אסור לכסות בו צואה תסתיים
The Gemara comments: Conclude that Rava is the one who said that a koy is similar to excrement, as Rava said: If one brought in earth to cover excrement with it, it is permitted to cover the blood of a bird with it; if he did bring in earth to cover the blood of a bird, it is prohibited to cover excrement with it. One intends to use the earth for the definite rather than the uncertain purpose, and likewise in the case of a koy. The Gemara summarizes: Indeed, conclude that this is the correct version of the opinions in the dispute.
רמי בריה דרב ייבא אמר כוי היינו טעמא דלא מכסינן גזירה משום התרת חלבו
§ Rami, son of Rav Yeiva, said a different reason: In the case of a koy, this is the reasoning for the halakha that one may not cover its blood: It is not because this action would constitute prohibited labor; rather, it is a rabbinic decree due to the permission of its prohibited fat. If one were to cover its blood, people might think that a koy is definitely an undomesticated animal, and it is well known that the fats of an undomesticated animal may be eaten, whereas those of a domesticated animal are prohibited.
אי הכי אפילו בחול נמי בחול אמרי לנקר חצרו הוא צריך
The Gemara challenges this: If so, even on a weekday as well, the blood of a koy should not be covered, due to this concern. The Gemara answers: On a weekday, people will say that he needs to clean his courtyard, and that he is covering the blood merely to keep his courtyard presentable, rather than to fulfill the mitzva of covering blood.
שחט באשפה מאי איכא למימר בא לימלך מאי איכא למימר
The Gemara asks: And if he slaughtered a koy in a dunghill, a place used for the disposal of refuse, what is there to say? It will be evident that he is not concerned about its cleanliness, and that he is attempting to perform the mitzva of covering blood. Alternatively, if he comes to consult a Sage concerning whether or not he should cover the blood of a koy on a weekday, what is there to say? If the owner of the koy is instructed to cover the blood, would he not come to the erroneous conclusion that its fats are permitted?
אלא בחול [אי נמי] מספקא אמרי ליה רבנן זיל טרח וכסי ביום טוב אי מספקא מי אמרי ליה רבנן זיל טרח וכסי
Rather, the Gemara answers: On a weekday, even if the matter is uncertain, the Sages nevertheless say to him: Go and take the trouble and cover it, as it involves the possible fulfillment of a mitzva. On a Festival, however, if there is uncertainty, would the Sages say to him: Go and take the trouble and cover it? If one was told to cover the blood on a Festival, this would indicate that a koy is definitely an undomesticated animal.
תני רבי זירא לא כוי בלבד אמרו אלא אפילו שחט בהמה חיה ועוף ונתערבו דמן זה בזה אסור לכסותו ביום טוב
Rabbi Zeira teaches the following baraita: Not only did the Sages say that the blood of a koy should not be covered on a Festival, but even if one slaughtered a domesticated animal, whose blood need not be covered, and also slaughtered an undomesticated animal or a fowl, whose blood must be covered, and their bloods became mingled together, it is prohibited to cover the mixture of blood on a Festival.
אמר רבי יוסי בר יאסיניאה לא שנו אלא שאין יכול לכסותו בדקירה אחת אבל יכול לכסותו בדקירה אחת מותר
Rabbi Yosei bar Yasinia said: They taught this halakha only in a case where one cannot cover the entire mixture by one thrust of a shovel. However, if he can cover it with one thrust, it is permitted. Since the entire amount of blood can be covered with a single action, it does not matter if one unnecessarily covers the blood of a domesticated animal while performing the mitzva of covering the blood of a fowl or an undomesticated animal.
פשיטא מהו דתימא נגזר דקירה אחת אטו שתי דקירות קמ"ל
The Gemara comments: It is obvious that this is the case; since he covers all the blood in a single action, clearly he performs a mitzva. The Gemara answers: This ruling is nevertheless necessary, lest you say that we should decree and prohibit even one thrust, due to the possibility that he might perform two thrusts. Therefore, Rabbi Yosei bar Yasinia teaches us that this concern is not taken into account.
אמר) רבה שחט צפור מערב יו"ט אין מכסין אותו ביו"ט
§ Rabba said: If one slaughtered a bird on the eve of a Festival, one may not cover its blood on the Festival itself.