Gemara

Ula bar Chinena - Beraisa: If the top of a Hadas was cut and (something resembling) a date grew on top, it is Kosher.

Question (R. Yirmeyah): If the top of a Hadas was cut before Yom Tov and a date grew on top on Yom Tov, what is the law?

Does Dichuy apply to Mitzvos (if something became Pasul for a Mitzvah, does it become permanently Pasul, even if the Pesul will go away)?

Question: Why didn't he settle the question from a Mishnah?

Mishnah: If one covered the blood (of a slaughtered bird or Chayah) and it became exposed, he need not cover it again. If the wind (blew dirt and) covered it, he must cover it.

Rabah bar bar Chanah: This is only if it became uncovered. If not, he is exempt.

Question: Even if it becomes uncovered, once the Mitzvah was lost, it should not return!

Answer (Rav Papa): This teaches that Ein Dichuy b'Mitzvos.

Answer (to Question ii): R. Yirmeyah knew that Ein Dichuy b'Mitzvos. He was unsure if the Tana was certain about this (and says Ein Dichuy even to be lenient), or if he was in doubt (and is stringent to require Kisuy in case the Halachah is that Ein Dichuy).

His question is not resolved.

Suggestion: Tana'im argue about this:

Beraisa - R. Eliezer b'Rebbi Tzadok: If one transgressed and picked berries off a Hadas (so there will be less berries than leaves, to make it Kosher) on Yom Tov, it is Pasul;

Chachamim say, it is Kosher.

Suggestion: R. Eliezer holds Yesh Dichuy b'Mitzvos, and Chachamim hold Ein Dichuy b'Mitzvos!

Rejection: No. All agree that Ein Dichuy b'Mitzvos. They argue about whether or not the four Minim must be tied together. (If they must, we learn Lulav from Sukah. Just like Sechach must be Kosher from the beginning, the Minim must be Kosher when they are tied together.) Alternatively, they agree that the Minim must be tied together, and argue about whether or not we learn Lulav from Sukah.

33b - Mishnah: If one diminished the berries (to be less than the leaves) it is Kosher.

Question: If he diminished them before binding the Minim (Dichuy does not apply), obviously it is Kosher;

Answer #1: We must say that he diminished them after binding them.

Inference: This shows that Dichuy me'Ikara (from the beginning) does not disqualify!

Rejection (and Answer #2): Indeed, he diminished them after binding them. However, the Tana holds that tying it is (not essential, rather,) mere preparation (therefore Dichuy does not apply).

Mishnah: One may not diminish them on Yom Tov.

Inference: If he diminished them on Yom Tov, it is Kosher.

Suggestion: If there was a majority of black (berries) from before Yom Tov, this is Dichuy me'Ikara. This shows that Dichuy me'Ikara is not Dichuy!

Rejection: No, on Yom Tov it became mostly black.

Suggestion: This shows that Nir'eh v'Nidcheh (something that was Kosher and then became Pasul) can become Kosher again (a bigger Chidush).

Rejection: Really, it was mostly black from before Yom Tov. Indeed, we may infer that Dichuy me'Ikara is not Dichuy, but we cannot resolve whether or not Nir'eh v'Nidcheh can become Kosher again.

Beraisa: One may not diminish the berries on Yom Tov;

R. Elazar b'Rebbi Shimon permits.

Question: This (makes it Kosher, it) is like fixing a Keli on Yom Tov!

Answer (Rav Ashi): The case is, he took the berries to eat (without intent to make it Kosher). R. Elazar holds like his father who permits Davar she'Eino Miskaven!

Question: But Abaye and Rava taught that R. Shimon agrees about a Pesik Reishei (it is as if he intended)!

Answer: The case is, he had another Hadas (therefore it is not like fixing a Keli).

Zevachim 34b - Mishnah: If a Kosher Kohen did Kabalah and gave it to a Pasul...(he returns it to a Kosher Kohen).

Question: We should say that Dichuy applies (the blood could not be offered while the Pasul was holding it!)

Answer #1 (Ravina citing Rava): Our Mishnah is like Chanan ha'Mitzri, who says that Dichuy does not apply even to a slaughtered animal.

Answer #2 (Rav Ashi): (All agree with our Mishnah.) Whenever it is b'Yado (he is able) to remedy the situation, Dichuy does not apply.

Rishonim

Rambam (Hilchos Lulav 8:5): If the top of a Hadas was cut it is Kosher.

Note: According to the Rambam the discussion of a date growing where it was cut is not according to Halachah.

Rambam (ibid.): If there were more black or red berries than leaves it is Pasul. If one diminished the berries (to be the minority) it is Kosher.

Question: The Rambam does not distinguish whether or not there were mostly berries when Yom Tov began! (Likewise, the Rosh and Tur did not distinguish!)

Answer #1 (Kesef Mishneh): Perhaps he holds that Dichuy does not apply to when one is able to fix it. The Gemara established the case to be that he has another Hadas, therefore removing berries from this to eat them is Davar she'Eino Miskaven and it is permitted. Therefore, even if blackened on Yom Tov (Nir'eh v'Nidcheh), it becomes Kosher again. The Gemara said that we cannot learn about Nir'eh v'Nidcheh before Rav Ashi explained how it is permitted to diminish. The conclusion is that Nir'eh v'Nidcheh can become Kosher again.

Rebuttal (Taz OC 646:6): The Rambam tells how one may fix the Hadas. This is not Davar she'Eino Miskaven! There is no indication in the Gemara that the question was resolved.

Answer #2 (Taz, ibid.): Rav Papa (33a) learned from Kisuy ha'Dam that Ein Dichuy b'Mitzvos (at all). R. Yirmeyah was unsure if this is to be stringent, or even to be lenient. We follow the clarity of Rav Papa without concern for the uncertainty of R. Yirmeyah. This is how the Rambam, Rosh and Tur learned. It is unlike the Ran (brought below).

Answer #3 (Bach 646 DH Hayu): Mid'Oraisa, Dichuy applies only to Korbanos. Regarding Mitzvos it is mid'Rabanan. Therefore, we are lenient about a Safek (Nir'eh v'Nidcheh, which was not resolved).

Answer #4 (Gra 646 DH O she'Liktan): We knew that Dichuy applies to Korbanos, even Dichuy me'Ikara. The question was whether or not Dichuy similarly applies to Mitzvos. Since we conclude that Dichuy me'Ikara is not Dichuy regarding Mitzvos, this shows that we do not learn Dichuy at all from Korbanos.

Note: The Gemara (33b) said that we can infer that Dichuy me'Ikara is not Dichuy, but we cannot learn about Nir'eh v'Nidcheh. Perhaps it means, from this case (of the Hadas) itself we cannot infer...

Answer #5 (R. Mano'ach): The Gemara (33a) said that all (R. Eliezer b'Rebbi Tzadok and Chachamim) agree that Ein Dichuy b'Mitzvos.

One may not diminish them on Yom Tov. If one transgressed and diminished them, or took them one by one to eat, it is Kosher.

Question (Kesef Mishneh): Why did the Rambam discuss one who transgressed and diminished? Why does he discuss one who took them one by one to eat? The same applies to one who took many at a time to eat them! However, this is permitted only if he has another Hadas. Why didn't the Rambam stipulate? According to the Magid Mishnah's text of the Rambam, 'or Acher (someone else, who has his own Hadasim) ate them', the latter question does not apply.

Rosh (3:11): If one diminished the berries it is Kosher. One may not diminish them on Yom Tov. If one transgressed and diminished them, it is Kosher.

Ran (15b DH v'Olsah): A Hadas with more berries is not considered totally b'Yado to fix, for if so we would say that even Nir'eh v'Nidcheh can become Kosher again. It is partially b'Yado, so Dichuy me'Ikara is not Dichuy. The same applies when the top was cut off, even though it is not b'Yado at all. Some say that in this case even Dichuy me'Ikara is Dichuy.

Tosfos (Zevachim 34b DH Kol): A Hadas with more berries is not called b'Yado (to fix it) because one may not diminish them on Yom Tov. When the wind blew dirt over blood this is not called b'Yado because there is no obligation to undo the Dichuy.

Question (R. Akiva Eiger on Mishnayos Sukah (20): The Gemara suggested (in the Reisha) that if he diminished the berries after tying the Minim together it is Kosher, and that Dichuy me'Ikara is not Dichuy. This was before Yom Tov, when it permitted to diminish, yet it is not considered b'Yado!

Answer (Aruch l'Ner Sukah 33b DH Tifshot): Rav Ashi distinguishes whether or not it is b'Yado, but Rava does not; this forced Rava to establish the Mishnah in Zevachim like an individual. The Gemara suggests that we can resolve the question according to Rava.

Rashi (33a DH Ovar): It is forbidden mid'Rabanan to diminish the berries on Yom Tov. Making the Hadas Kosher resembles fixing a Keli.

Riva (brought in Mordechai 747): It is forbidden mid'Oraisa to diminish the berries on Yom Tov.

Rebuttal (Kaf ha'Chayim OC 646:14): We find that cutting off a wart (to make a Kohen or Korban Kosher) is permitted in the Mikdash because it is only mid'Rabanan, and Ein Shevus b'Mikdash (Eruvin 103a-b).

Note: Chachamim permit cutting a moist wart only with a Keli. The Kaf ha'Chayim infers from the Heter to cut by hand that being Machshir is not a Melachah. With a Keli it is a Toldah mid'Oraisa of shearing. Perhaps the Riva understands that being Machshir is a Melachah. It is permitted by hand because this is a Shinuy!

Tosfos (Sukah 33b DH Modeh): When one has another Hadas he need not fix this, so even if it is fixed it is Melachah she'Einah Tzerichah l'Gufah. R. Shimon normally forbids this mid'Rabanan; for the sake of the Mitzvah he permits here. Rashi (DH Lo) says that when he does not need this Hadas he did not fix anything.

Poskim

Shulchan Aruch (OC 646:2): If there were more black or red berries than leaves it is Pasul. If one diminished the berries (to be the minority) it is Kosher. One may not diminish them on Yom Tov. If one transgressed and diminished them, or took them one by one to eat, it is Kosher.

Question (Taz 5): The Kesef Mishneh did not understand these words ('one by one') and preferred the Magid Mishnah's text. Why did he copy a text he did not understand into the Shulchan Aruch?!

Mishnah Berurah (8): It is permitted only for someone else to eat the berries, or the owner himself if he has other Hadasim. Then it is a Pesik Reishei d'Lo Nicha Lei.

Bi'ur Halachah (DH Ovar): The Rif, Rambam and Rosh did not explicitly permit Nir'eh v'Nidcheh. Many Rishonim explicitly forbid this, so one should be stringent.

Kaf ha'Chayim (18): It is better to be stringent if possible. But if one has no other Hadas he may rely on the Shulchan Aruch and numerous Poskim including the Bach, Taz, Gra and Eliyahu Rabah, who are lenient.