Shabbat 132

שכן אם עבר זמנה בטלה אלא היינו טעמא דרבי אליעזר דאמר קרא וביום השמיני ימול בשר ערלתו ואפילו בשבת

in each, as if its time passed, it is void, unlike the mitzva of circumcision, which can be fulfilled at a later date if the child is not circumcised on the eighth day. Rather, this is the reason for the opinion of Rabbi Eliezer, as the verse says: “And on the eighth day the flesh of his foreskin shall be circumcised” (Leviticus 12:3), indicating that he is circumcised on the eighth day even if it falls on Shabbat.

וליכתוב רחמנא במילה וליתו הנך וליגמור מיניה משום דאיכא למיפרך מה למילה שכן נכרתו עליה שלש עשרה בריתות:

The Gemara asks: And let the Torah write this principle only with regard to the mitzva of circumcision, and let these other mitzvot come and derive their halakhot from it. The Gemara answers: Because this suggestion can be refuted: What is unique about the mitzva of circumcision? That thirteen covenants were established over it, as the word covenant is mentioned thirteen times in the passage dealing with the circumcision of Abraham (Genesis 17). Owing to its great significance, other mitzvot cannot be derived from it.

עד כאן לא פליגי רבנן עליה אלא במכשירי מילה אבל מילה גופה דברי הכל דוחה שבת מנלן אמר עולא הלכה וכן אמר רבי יצחק הלכה

The Gemara departs from the facilitators of circumcision to the halakha of circumcision itself and asks: The Rabbis only disagree with Rabbi Eliezer with regard to actions that facilitate circumcision, which, in their view, do not override Shabbat; however, with regard to circumcision itself, everyone agrees that it overrides Shabbat. From where do we derive this halakha? Ulla said: This is a halakha transmitted to Moses from Sinai, but there is no biblical basis for it. And so too, Rabbi Yitzḥak said: It is a halakha transmitted to Moses from Sinai.

מיתיבי מניין לפיקוח נפש שדוחה את השבת רבי אלעזר בן עזריה אומר מה מילה שהיא אחת מאיבריו של אדם דוחה את השבת קל וחומר לפיקוח נפש שדוחה את השבת

The Gemara raises an objection from that which was taught in the Tosefta: From where is it derived that saving a life overrides Shabbat? Rabbi Elazar ben Azarya says it is derived from the mitzva of circumcision: Just as circumcision, which pertains to only one of a person’s limbs, overrides Shabbat, all the more so it is an a fortiori inference that saving a life, which is a mitzva that pertains to the entire person, overrides Shabbat.

ואי סלקא דעתך הלכה קל וחומר מהלכה מי אתי והתניא אמר לו רבי אלעזר (בן עזריה) עקיבא עצם כשעורה מטמא הלכה ורביעית דם קל וחומר ואין דנין קל וחומר מהלכה

And if it should enter your mind to say that circumcision may be performed on Shabbat based on a halakha transmitted to Moses from Sinai, is an a fortiori inference derived from a halakha transmitted to Moses from Sinai? Wasn’t it taught explicitly in a baraita that an a fortiori inference cannot be derived from a halakha transmitted to Moses from Sinai? Rabbi Akiva sought to derive that a nazirite who comes into contact with a quarter log of blood from a corpse becomes ritually impure and is required to shave his hair. He sought to do this based on an a fortiori inference from the halakha of the bone from a dead person the size of a grain of barley, as he had a received tradition that a nazirite is required to shave his hair due to that contact. Rabbi Elazar ben Azarya said to him: Akiva, the halakha that a bone the size of a grain of barley transmits ritual impurity is a halakha transmitted to Moses from Sinai, and you would derive from it that a quarter of a log of blood transmits ritual impurity based upon an a fortiori inference, and one does not derive an a fortiori inference from a halakha transmitted to Moses from Sinai. The Tosefta explicitly states that Rabbi Elazar ben Azarya himself derived an a fortiori inference from the halakha of circumcision on Shabbat. Clearly, then, it is derived from the Torah itself and not from a halakha transmitted to Moses from Sinai.

אלא אמר רבי אלעזר אתיא אות אות

Rather, Rabbi Elazar said: This halakha is derived by means of a verbal analogy between the word sign that appears with regard to circumcision: “And you shall be circumcised in the flesh of your foreskin; and it shall be a sign of the covenant between Me and you” (Genesis 17:11), and sign that appears with regard to Shabbat: “However, you shall keep My Shabbatot, for it is a sign between Me and you throughout your generations” (Exodus 31:13). From this verbal analogy, it is derived that circumcision, which is a sign, may be performed even on Shabbat, which is itself a sign.

אלא מעתה תפילין דכתיב בהן אות לידחי שבת

The Gemara asks: But if what you say is so, phylacteries, with regard to which the term sign is also written: “And it shall be for a sign on your hand and for frontlets between your eyes” (Exodus 13:16), should also override Shabbat, and they should be donned on that day.

אלא אתיא ברית ברית

Rather, this principle is derived by means of a different verbal analogy from the word covenant that appears with regard to circumcision: “And you shall be circumcised in the flesh of your foreskin; and it shall be a sign of the covenant between Me and you” (Genesis 17:11), and the word covenant that appears with regard to Shabbat: “The children of Israel shall keep the Shabbat, to observe the Shabbat throughout their generations for a perpetual covenant” (Exodus 31:16).

גדול דכתיב ביה ברית לידחי שבת

The Gemara raises a difficulty: If this is so, then the circumcision of an adult should also be permitted on Shabbat and it should not be limited to a child on the eighth day, as the term covenant is written with regard to him as well, as it applies to any Jewish male not yet circumcised. Therefore, let his circumcision override Shabbat. The halakha, however, is that only circumcision at its proper time on the eighth day overrides Shabbat.

אלא אתיא דורות דורות

Rather, this halakha is derived by means of a verbal analogy between the word generations that appears with regard to Shabbat: “Throughout their generations for a perpetual covenant” (Exodus 31:16), and the word generations that appears with regard to circumcision: “And I shall establish My covenant between Me and you, and between your seed after you throughout their generations, for an everlasting covenant” (Genesis 17:7).

ציצית דכתיב ביה דורות לידחי שבת

The Gemara asks: If so, let ritual fringes too, with regard to which the term generations is also written, override Shabbat, and it should be permitted to affix ritual fringes to a garment on Shabbat.

אלא אמר רב נחמן בר יצחק דנין אות ברית ודורות מאות ברית ודורות לאפוקי הנך דחד חד הוא דכתיב בהן

Rather, Rav Naḥman bar Yitzḥak said: This halakha is derived not from one common word alone, but one derives it based upon the three words sign, covenant, and generations that appear with regard to circumcision, from sign, covenant, and generations that appear with regard to Shabbat, to the exclusion of these, i.e., ritual fringes and phylacteries, that with regard to each of them, one of these is written but not all three words together.

ורבי יוחנן אמר אמר קרא ביום ביום אפילו בשבת

And Rabbi Yoḥanan said: The verse says: “And on the eighth day…shall be circumcised” (Leviticus 12:3), which means that the child is circumcised on the eighth day whenever it occurs, even on Shabbat.

אמר ליה ריש לקיש לרבי יוחנן אלא מעתה מחוסרי כפרה דכתיב בהו ביום הכי נמי דדחו שבת ההוא מיבעי ליה ביום ולא בלילה

Reish Lakish said to Rabbi Yoḥanan: But if what you say is so, then, with regard to those lacking atonement, such as a zav or a healed leper, who must after their immersion still bring an atonement offering in order to complete their purification process, with regard to whom the term on the day is also written, as in the verse: “And on the eighth day he shall take two he-lambs without blemish, and one ewe-lamb of the first year without blemish” (Leviticus 14:10), sacrificing their atonement offerings should also override Shabbat. Rabbi Yoḥanan responded: That verse is necessary to teach that the sacrifice must be brought during the day and not at night.

האי נמי מיבעי ליה ביום ולא בלילה ההוא מבן שמנת ימים נפקא

Reish Lakish asked: This verse with regard to the mitzva of circumcision is also necessary to teach that circumcision must be performed during the day and not at night. Rabbi Yoḥanan replied: That is derived from a different verse, which states: “And he that is eight days old shall be circumcised among you throughout your generations” (Genesis 17:12). That circumcision must take place during the day is derived from that verse.

האי נמי מביום צוותו נפקא

Reish Lakish says: That matter, that the atonement offering must be sacrificed during the day, can also be derived from a different verse, as it is stated: “This is the law of the burnt-offering, of the meal-offering, and of the sin-offering, and of the guilt-offering, and of the consecration-offering, and of the sacrifice of the peace-offerings; which the Lord commanded Moses at Mount Sinai on the day He commanded the children of Israel to present their offerings to the Lord in the wilderness of Sinai” (Leviticus 7:37–38), and from here it is derived that all offerings are sacrificed by day and not at night.

אף על גב דנפקא מביום צוותו אצטריכא סלקא דעתך אמינא הואיל וחס רחמנא עליה לאתויי בדלות בלילה נמי ליתי קא משמע לן

The Gemara answers: Although this halakha is derived from: “On the day He commanded,” an additional source is necessary for those lacking atonement. It might have entered your mind to say that since the Torah shows him mercy by allowing him to bring an offering of poverty, as if one cannot afford to sacrifice the regular atonement offering, the Torah enables him to sacrifice a less costly one, let him also bring it at night, as perhaps the Torah shows him mercy and allows him to hasten his atonement. Therefore, it teaches us that he too must bring his offering only by day and not at night.

מתקיף לה רבינא אלא מעתה יהא זר כשר בהן ויהא אונן כשר בהן הא אהדריה קרא

Ravina strongly objects to this reasoning: But if what you say is so, that the Torah has compassion on a person lacking atonement and is lenient with regard to the halakhot of the atonement offering, a non-priest should be fit to sacrifice them, and similarly, a priest who is an acute mourner, i.e., one whose relative died that same day and has not yet been buried, should be fit to sacrifice them. The Gemara answers: The verse has restored this. The additional verse that teaches that even one lacking atonement must sacrifice during the day, also teaches that the Torah was lenient with regard to this offering only in the ways explicitly stated in the Torah.

רב אחא בר יעקב אמר אמר קרא שמיני שמיני אפילו בשבת

Rav Aḥa bar Ya’akov said: There is a different proof from the Torah that circumcision is performed even on Shabbat, for the verse said: “On the eighth day,” underscoring that circumcision is performed specifically on the eighth day and indicating that it is performed even on Shabbat.

האי שמיני מיבעי ליה למעוטי שביעי שביעי מבן שמנת ימים נפקא

The Gemara raises a difficulty: This usage of the term eighth is necessary to exclude the seventh day, i.e., a child may not be circumcised before the eighth day. The Gemara answers: The fact that one may not circumcise on the seventh day is derived from a different verse, as it is stated: “And he that is eight days old shall be circumcised among you throughout your generations” (Genesis 17:12).

ואכתי מיבעי ליה חד למעוטי שביעי וחד למעוטי תשיעי דאי מחד הוה אמינא שביעי הוא דלא מטא זמניה אבל משמיני ואילך זמניה הוא אלא מחוורתא כדרבי יוחנן

The Gemara raises a further difficulty: Both verses are still necessary, one to exclude the seventh day and one to exclude the ninth day. As if it were derived from one verse alone, I would have said: It is on the seventh day that one may not circumcise, since the time to circumcise this child has not yet arrived and the obligation of circumcision is not yet in effect; however, from the eighth day and onward is its time, and therefore it is permissible to postpone a circumcision until the ninth day. No answer was found to this question, and the Gemara concludes: Rather, the derivation is clear according to Rabbi Yoḥanan.

תניא כוותיה דרבי יוחנן ודלא כרב אחא בר יעקב שמיני ימול אפילו בשבת ומה אני מקיים מחלליה מות יומת בשאר מלאכות חוץ ממילה או אינו אלא אפילו מילה ומה אני מקיים שמיני ימול חוץ משבת תלמוד לומר ביום אפילו בשבת

It was taught in a baraita in accordance with the opinion of Rabbi Yoḥanan and not in accordance with the opinion of Rav Aḥa bar Ya’akov, as the tanna interprets the phrase: “On the eighth day he shall be circumcised” to mean that the circumcision must be performed even on Shabbat. And how do I fulfill the prohibition against performing prohibited labor explicit in the Torah in the verse: “And you shall guard the Shabbat, for it is holy to you; he who desecrates it shall surely die” (Exodus 31:14)? That is referring to other prohibited labors besides circumcision. The tanna questions his previous statement: Or perhaps that is not the case, and the prohibition of performing prohibited labor on Shabbat includes even circumcision, and, on the contrary, how do I fulfill the verse: “On the eighth day he shall be circumcised”? It applies when the eighth day is any day other than Shabbat. The verse states: “On the day,” meaning on that very day when he turns eight days old, even on Shabbat. The tanna of this baraita rejects Rav Aḥa bar Ya’akov’s proof and accepts Rabbi Yoḥanan’s assertion that the phrase “On the day” conclusively establishes that circumcision is performed even on Shabbat.

אמר רבא האי תנא מעיקרא מאי קא ניחא ליה ולבסוף מאי קא קשיא ליה

With regard to this baraita, Rava said: Initially, what did this tanna find acceptable, and ultimately, what did he find difficult? Initially he suggested that: “On the eighth day he shall be circumcised” is a valid source for the fact that circumcision overrides Shabbat, but ultimately, he deemed that difficult and turned to an alternative source, yet provided no reason, neither for his initial statement nor for his second statement.

הכי קאמר שמיני ימול אפילו בשבת ומה אני מקיים מחלליה מות יומת בשאר מלאכות חוץ ממילה אבל מילה דחיא

Rather, we can explain that this is what he is saying: “On the eighth day he shall be circumcised” applies even on Shabbat. And how do I fulfill: “He who desecrates it shall surely die”? That is referring to the other prohibited labors besides circumcision; however, circumcision overrides Shabbat.

מאי טעמא קל וחומר הוא ומה צרעת שדוחה את העבודה

What is the reason for this? It is derived by means of an a fortiori inference: Just as leprosy, which overrides the Temple service, as a priest who is a leper may not serve in the Temple and it is prohibited to cut off the symptoms of leprosy,

ועבודה דוחה את השבת מילה דוחה אותה שבת שנדחית מפני העבודה אינו דין שתהא מילה דוחה אותה

and the Temple service overrides Shabbat, as Shabbat offerings are sacrificed at their appointed time, and nevertheless circumcision overrides leprosy, i.e., if there were symptoms of leprosy on the foreskin of the baby, one circumcises the child even though he thereby violates the prohibition to cut off symptoms of leprosy; therefore, with regard to Shabbat, which is overridden by the Temple service, is it not logical that circumcision, which is so stringent that it overrides leprosy, overrides Shabbat as well? This was the tanna’s reasoning at the outset.

ומאי או אינו דקאמר הדר אמר וממאי דצרעת חמורה דילמא שבת חמורה שכן יש בה עונשין ואזהרות הרבה (אי נמי) וממאי משום דחמירא צרעת היא דילמא משום גברא הוא דלא חזי ומה אני מקיים שמיני ימול חוץ משבת תלמוד לומר ביום אפילו בשבת:

And what was the reason the tanna said: Or perhaps, and questioned his previous statement? He reconsidered and said: And from where do we know that leprosy is more stringent than Shabbat? Perhaps Shabbat is more stringent, as it includes the severe punishments of karet and execution by stoning, and numerous warnings pertaining to it throughout the Torah. Alternatively, and from where do we know that the reason the Temple service does not override the prohibition of leprosy is specifically because leprosy is more stringent than the Temple service? Perhaps the Temple service does not override the prohibition of leprosy because a man afflicted with leprosy is unfit to perform the Temple service and not due to the stringency of the prohibition to remove symptoms of leprosy from one’s body. And if so, how do I establish the verse: “And on the eighth day the flesh of his foreskin shall be circumcised” (Leviticus 12:3)? That it applies to days other than Shabbat. Consequently, the tanna cited additional proof from that which the Torah states: “On the day,” indicating that circumcision is performed even on Shabbat.

תנו רבנן מילה דוחה את הצרעת בין בזמנה בין שלא בזמנה יום טוב אינה דוחה אלא בזמנה בלבד

The Sages taught: Circumcision overrides leprosy. The foreskin is cut even if it has symptoms of leprosy on it, despite the fact that there is a Torah prohibition to cut off symptoms of leprosy. This is the halakha both when the circumcision takes place at its appointed time, on the eighth day, or when it is not performed at its appointed time but after the eighth day. However, circumcision overrides a Festival only when performed at its appointed time.

מנהני מילי דתנו רבנן ימול בשר ערלתו ואף על פי שיש שם בהרת יקוץ ומה אני מקיים השמר בנגע הצרעת בשאר מקומות חוץ ממילה

The Gemara asks: From where are these matters derived? As the Sages taught in a baraita with regard to the verse: “And on the eighth day the flesh of his foreskin shall be circumcised” (Leviticus 12:3), since this verse is stated in general terms, it teaches that even though there is a bright white leprous spot there, he should cut it. And how do I establish the verse: “Take care with regard to the plague of leprosy to take great care and to perform in accordance with all that the priests, the Levites, instruct you; as I commanded them you shall take care to perform” (Deuteronomy 24:8)? Does usage of the term “take care” indicate that there is a negative mitzva that prohibits cutting off symptoms of leprosy? We establish this prohibition as applying in other places, other than the place of a circumcision.

או אינו אלא אפילו מילה ומה אני מקיים ימול בשר ערלתו בזמן שאין בה בהרת תלמוד לומר בשר ואף על פי שיש שם בהרת

The tanna asks: Or perhaps that is not the case; rather, this prohibition applies even in the place of circumcision, and how do I validate the verse: “The flesh of his foreskin shall be circumcised”? It applies when there is no bright white leprous spot on the foreskin. So that we will not interpret the verse that way, the verse states the superfluous word flesh. It would have been sufficient to state: His foreskin shall be circumcised, but instead the verse stated: “The flesh of his foreskin shall be circumcised,” indicating that the foreskin must be removed even though there is a bright white spot there.

אמר רבא האי תנא מעיקרא מאי ניחא ליה ולבסוף מאי קשיא ליה

Rava said: Initially, what did this tanna find acceptable, and ultimately, what did he find difficult? At first he assumed that the mitzva of circumcision is more stringent, but he ultimately rejected this assumption with no explanation.

הכי קאמר ימול בשר ערלתו ואף על פי שיש בהרת ומה אני מקיים השמר בנגע הצרעת בשאר מקומות חוץ ממילה אבל מילה דוחה את הצרעת מאי טעמא דאתיא מקל וחומר ומה שבת חמורה מילה דוחה אותה צרעת לא כל שכן

Rather, this is what he is saying: Initially he held that the phrase: The flesh of his foreskin shall be circumcised teaches that it is permitted to remove the foreskin even though there is a bright white spot there. And how do I validate the following verse: Take care with regard to the plague of leprosy? It applies in other places, aside from the place of circumcision, but circumcision overrides leprosy. What is the reason for this? It is derived by means of an a fortiori inference: Just as Shabbat is stringent and nevertheless circumcision overrides it, all the more so that circumcision overrides leprosy, which is less stringent than Shabbat.

ומאי או אינו דקאמר הדר קאמר ממאי דשבת חמירא דילמא צרעת חמירא שכן דוחה את העבודה ועבודה דוחה את השבת תלמוד לומר בשר ואף על פי שיש שם בהרת

And what was the reason for the term or perhaps that the tanna is saying to question his previous statement? He reconsidered and said: From where do we know that Shabbat is more stringent? Perhaps leprosy is more stringent, as leprosy overrides the Temple service, as stated earlier, and the Temple service overrides Shabbat. Therefore, the verse states the additional word flesh, to teach that the foreskin is removed even though there is a bright white leprous spot there.

לישנא אחרינא מילה דוחה את הצרעת מאי טעמא דאתי עשה ודחי לא תעשה ומאי או אינו דקאמר הדר קאמר אימר דאמרינן דאתי עשה ודחי את לא תעשה לא תעשה גרידא האי עשה ולא תעשה הוא ומה אני מקיים ימול בשר ערלתו בזמן שאין בה בהרת תלמוד לומר בשר ואף על פי שיש שם בהרת

The Gemara cites another version of Rava’s comments. Initially the tanna thought that circumcision overrides leprosy. What is the reason for this? He relied on the principle that a positive mitzva comes and overrides a negative mitzva. And what was the reason the tanna is saying: Or perhaps to question his previous statement? He reconsidered and said: Say that we say that a positive mitzva comes and overrides a negative mitzva when there is a negative mitzva alone. However, this cutting off leprosy is prohibited by both a positive mitzva and a negative mitzva. And how do I establish the verse: The flesh of his foreskin shall be circumcised? It applies only when there is no bright white spot on the foreskin. Therefore, the verse states the additional word flesh in order to emphasize that the foreskin is removed, even though there is a bright white spot there.

תינח גדול דכתיב בהו בשר קטן נמי כתיב ביה בשר בינוני מנלן

The Gemara questions the derivation from the word flesh: This works out well with regard to the circumcision of an adult who has not yet been circumcised, as the word flesh is written with regard to adults in the verse: “And an uncircumcised male who will not circumcise the flesh of his foreskin, that soul shall be cut off from its people; My covenant he has broken” (Genesis 17:14). Similarly, it works out well with regard to a minor who is circumcised on the eighth day, as the superfluous word flesh is also written with regard to him. However, with regard to a person at an intermediate stage of life, i.e., a child who was not circumcised on the eighth day but has not yet reached majority, from where do we derive that his circumcision overrides leprosy? The Torah explicitly mandates his circumcision: “Circumcise for yourselves every male” (Genesis 17:10). However, that verse does not employ the term flesh.

אמר אביי אתיא מביניא מגדול לא אתיא שכן ענוש כרת מקטן לא אתיא שכן מילה בזמנה הצד השוה שבהן שכן נימולין ודוחין את הצרעת אף כל שנימולין דוחין את הצרעת

Abaye said: It is derived from a combination of the two sources about the status of a child at the intermediate stage, from the common denominator between an eight-day-old and one who reached majority. From an adult alone, the halakha with regard to an intermediate child cannot be derived, as an adult is punishable by karet if he fails to circumcise himself, but an intermediate child is not punishable by karet. Likewise, from the case of an eight-day-old child, the case of an intermediate child cannot be derived; since the circumcision at its time overrides Shabbat it may also override leprosy. However, the common denominator between an eight-day-old and an adult is that they are circumcised and their circumcision overrides leprosy. So too, all who are circumcised, including those in the intermediate stage, override leprosy.

רבא אמר מילה בזמנה דוחה לא צריכא קרא מקל וחומר אתיא ומה שבת דחמירא דוחה צרעת לא כל שכן

Rava said: No verse is required to teach that circumcision at its appointed time overrides leprosy, as it is derived by means of an a fortiori inference: Just as circumcision overrides Shabbat, which is more stringent than leprosy, all the more so that circumcision overrides leprosy.

אמר ליה רב ספרא לרבא ממאי דשבת חמירא דילמא צרעת חמירא שכן דוחה את העבודה ועבודה דוחה את השבת התם לאו משום דחמירא צרעת אלא משום דגברא הוא דלא חזי אמאי ויקוץ בהרתו ויעבוד מחוסר טבילה הוא

Rav Safra said to Rava: From where do we know that Shabbat is more stringent? Perhaps leprosy is more stringent, as leprosy overrides the Temple service, and the Temple service overrides Shabbat. Rava answered: There, when leprosy overrides the Temple service, it is not because leprosy is more stringent; rather, it is because the man afflicted with leprosy is unfit for the Temple service. Rav Safra asked: Why is he unfit? Let him cut off his bright white leprous spot and serve. Rava answered: He would remain unfit to serve, as he is lacking immersion. In order to purify himself for service in the Temple, he must immerse himself and wait until the following day. In the meantime he is unfit.

תינח נגעים טמאים נגעים טהורים מאי איכא למימר

Rav Safra raised a difficulty: It works out well if we are referring to impure symptoms of leprosy, as even one who removes them must immerse afterward. However, with regard to pure symptoms of leprosy, there is a prohibition to cut off the symptoms even though there is no impurity. They have the legal status of blemishes that invalidate a priest from serving until it is cured. Once the bright white spot is removed, he may immediately serve in the Temple without immersion. What is there to say in that case?

אלא אמר רב אשי היכא אמרינן דאתי עשה ודחי לא תעשה כגון מילה בצרעת אי נמי ציצית וכלאים דבעידנא דמתעקר לאו קא מוקים עשה הכא בעידנא דמתעקר ללאו לא קא מוקים עשה

Rather, Rav Ashi said that this is the reason that leprosy overrides the Temple service: Where do we say that a positive mitzva overrides a negative mitzva? It is in cases like circumcision in a case of leprosy, or alternatively, ritual fringes and diverse kinds of wool and linen, as at the time the negative mitzva is uprooted, the positive mitzva is fulfilled in the very same action, e.g., when the ritual fringes are woolen and will be attached to a linen garment, a prohibited mixture is created. However, here, in the case of a person afflicted with pure symptoms of leprosy cutting off his symptoms to enable his involvement in the Temple service, it is different, at the time the negative mitzva is uprooted, the positive mitzva is not yet fulfilled, as cutting off the symptoms is only a preliminary action that enables him to serve. In that case, the positive mitzva does not override the negative one.

והא דרבא ורב ספרא

The Gemara points out that this disagreement between Rava and Rav Safra