הא בכולה הא במקצתה:
this mishna, where it states that if the etrog was peeled it is unfit, is in a case where all of it was peeled. That statement of Rava that if it was peeled it is fit is in a case where only part of it was peeled.
נסדק ניקב: תני עולא בר חנינא ניקב נקב מפולש במשהו ושאינו מפולש בכאיסר
The mishna continues discussing the halakha of an etrog that was split or pierced. Ulla bar Ḥanina taught: An etrog that was pierced with a hole that completely goes through its body is unfit with any size hole. If the hole does not completely go through the etrog, it is unfit only with a hole the size of an issar coin.
בעי רבא נולדו באתרוג סימני טרפה מהו מאי קמיבעיא ליה אי נקלף תנינא אי נסדק תנינא אי ניקב תנינא
Rava raised a dilemma: If signs of a tereifa developed in the etrog, what is its halakhic status? The Gemara clarifies: What is the dilemma that he is raising? There are similarities between the halakhot of the etrog in the mishna and some of the halakhot of a tereifa, a bird or animal with a condition that will lead to its death within a year. If it is the case where the etrog was peeled, we already learned that case. If it is the case where the etrog was split, we learned that case as well. And if it is the case where the etrog was pierced, we learned that too. After ruling out those defects, the question remains: With regard to what is Rava’s dilemma?
כי קא מיבעיא ליה כדעולא אמר רבי יוחנן ריאה שנשפכה כקיתון כשרה ואמר רבא והוא דקיימא סימפונהא הא לא קיימי סימפונהא טרפה הכא מאי דלמא התם הוא דלא שליט בה אוירא הדר בריא אבל הכא דשליט בה אוירא סרוחי מסרחת או דלמא לא שנא
The Gemara answers: When he raises the dilemma, it is with regard to a case like that which Ulla said that Rabbi Yoḥanan said: A lung whose contents can be poured like a pitcher, i.e., whose tissue dissolved to the point of liquefaction, is not a sign of tereifa, and the animal is kosher. And Rava said: And that is the halakha only where the bronchia are intact. However, if the bronchia are not intact, it is a sign of tereifa. The dilemma here is with regard to a comparable situation in an etrog, i.e., an etrog that liquefied from within: What is its halakhic status? Perhaps it is there, in the case of the lung, where the air does not affect it since it is completely enclosed in the body, that the lungs can recover, and that is why it is not a tereifa. However, here, in the case of the etrog, where the air affects it, it inevitably decays and spoils and therefore it is a tereifa. Or, perhaps the case of the etrog is no different.
ת"ש אתרוג תפוח סרוח כבוש שלוק כושי לבן ומנומר פסול אתרוג ככדור פסול ויש אומרים אף התיום אתרוג הבוסר ר"ע פוסל וחכמים מכשירין גדלו בדפוס ועשאו כמין בריה אחרת פסול
The Gemara answers: Come and hear a resolution to this dilemma based on that which was taught in a baraita. An etrog that is tafuaḥ, saruaḥ, pickled, boiled, a black Cushite etrog, a white etrog, or a speckled etrog is unfit. An etrog shaped like a ball is unfit, and some say even a twin, conjoined, etrog is unfit. With regard to an etrog that is unripe, Rabbi Akiva deems it unfit, and the Rabbis deem it fit. If he grew the etrog in a mold and shaped it to appear like a different entity, and it is no longer shaped like an etrog, it is unfit.
קתני מיהת תפוח סרוח מאי לאו תפוח מבחוץ וסרוח מבפנים לא אידי ואידי מבחוץ ולא קשיא הא דתפח אע"ג דלא סרח הא דסרח אע"ג דלא תפח
In any event, it teaches that an etrog that is tafuaḥ or saruaḥ is unfit. What, is it not that tafuaḥ means that it decayed on the outside and saruaḥ means that it decayed on the inside? The Gemara rejects this explanation: No, both this and that are referring to decay on the outside. And this apparent redundancy is not difficult, as this case, tafuaḥ, is where it swelled even though it did not decay, and that case, saruaḥ, is where it decayed even though it did not swell.
אמר מר אתרוג כושי פסול והתניא כושי כשר דומה לכושי פסול אמר אביי כי תנן נמי מתני' דומה לכושי תנן רבא אמר לא קשיא הא לן והא להו
The Master said in the baraita cited above: A Cushite etrog is unfit. The Gemara asks: But isn’t it taught in a different baraita: A Cushite etrog is fit, but an etrog that is similar to a Cushite etrog is unfit. Abaye said: When we learned this halakha in the mishna that it is unfit, too, we learned it not in reference to an actual Cushite etrog, but rather in reference to one that is similar to a Cushite etrog. Rava said: Actually, the mishna is referring to a Cushite etrog, and nevertheless, it is not difficult; this, the halakha that it is unfit, is for us in Babylonia because our etrogim are typically light, and the dark Cushite etrogim are conspicuously different. And that, the halakha that it is fit, is for them in Eretz Yisrael, whose etrogim are typically dark. In Eretz Yisrael the dark Cushite etrog is not conspicuously different, and it is therefore fit.
אתרוג הבוסר ר"ע פוסל וחכמים מכשירין אמר רבה ר' עקיבא ור"ש אמרו דבר אחד ר"ע הא דאמרן ר"ש מאי היא (דתניא) ר"ש פוטר את האתרוגים בקוטנן
It was also taught in the baraita: With regard to an unripe etrog, Rabbi Akiva deems it unfit, and the Rabbis deem it fit. Rabba said: Rabbi Akiva and Rabbi Shimon said one and the same statement. The Gemara elaborates: The statement of Rabbi Akiva is that which we said; an unripe etrog is unfit. Rabbi Shimon, what is his statement? It is as it is taught in a baraita: Rabbi Shimon exempts etrogim from the requirement to be tithed while in their small state. Apparently, Rabbi Shimon, too, holds that an unripe etrog is not a fruit.
א"ל אביי דלמא לא היא עד כאן לא קאמר ר"ע הכא דבעינן הדר וליכא אבל התם כרבנן סבירא ליה
Abaye said to Rabba: Perhaps that is not the case and they do not share the same opinion. Rabbi Akiva stated his opinion only here, with regard to an unripe etrog, as we require beauty [hadar] in an etrog and there is none in the case of an unripe etrog due to its color or small size; however, there, with regard to tithes, perhaps he holds in accordance with the opinion of the Rabbis that one is obligated to tithe even a half-ripe etrog.
אי נמי עד כאן לא קאמר ר"ש התם אלא דכתיב (דברים יד, כב) עשר תעשר את כל תבואת זרעך כדרך שבני אדם מוציאין לזריעה אבל הכא כרבנן סבירא ליה
Alternatively, Rabbi Shimon stated his opinion only there with regard to the exemption of an unripe etrog from tithes, as it is written: “You shall surely tithe all the produce of your planting, which is brought forth in the field year by year” (Deuteronomy 14:22). From that verse it is derived that the obligation to tithe applies only to produce that has developed to the point where it is typical for people to take it out to the field for sowing; one is not obligated to tithe unripe fruit that is not suitable for planting. However, perhaps here he holds in accordance with the opinion of the Rabbis, who disagree with Rabbi Akiva and would deem an unripe etrog fit.