Gemara

(Beraisa - R. Akiva) Question: Why does it say "be'Charish uva'Katzir Tishbos"? "Sadcha Lo Sizra..." already forbids plowing and reaping in Shemitah! Rather, this forbids plowing in Erev Shemitah, and gives Kedushas Shemitah to Peros reaped in Motzei Shemitah that were a third grown in Shemitah.

Avodah Zarah 73b (Mishnah): The general rule is, Min b'Mino (a mixture of similar species), it (Yayin Nesech) forbids b'Mashehu (any amount). Lo b'Mino (with a different species), it forbids b'Nosen Ta'am (if it gives taste).

(Rav and Shmuel): All forbidden foods, if mixed b'Mino, forbid b'Mashehu. If mixed Lo b'Mino, they forbid b'Nosen Ta'am;

The general rule of the Mishnah includes all forbidden foods.

(R. Yochanan and Reish Lakish): Only Tevel and Yayin Nesech forbid b'Mashehu Min b'Mino, and Lo b'Mino, b'Nosen Ta'am. Everything else forbids b'Nosen Ta'am, whether b'Mino or Lo b'Mino;

The general rule of the Mishnah includes Tevel.

Nedarim 57b (Yishmael of Yama) Question: If an onion was uprooted in Shemitah and planted in the eighth year, and the added growth is more than the bulb, do we say that the added growth is permitted, but the bulb is forbidden (must be eaten with Kedushas Shemitah)?

58a - Answer (Beraisa - R. Shimon): There is no Shi'ur (for Bitul) for any Davar she'Yesh Lo Matitrim (an Isur that can be permitted in another situation), such as Tevel, Ma'aser Sheni... For every Davar she'Ein Lo Matirim, such as Terumah, Chalah, Orlah... Chachamim fixed a Shi'ur (for Bitul).

Chachamim: Shemitah is never permitted, yet it is never Batel! A Mishnah says that any amount of Shemitah Peros forbids b'Mino.

R. Shimon: (In that Mishnah) I said only regarding Bi'ur. Eating depends on Nosen Ta'am.

Rejection: Perhaps here also we are stringent to say that the bulb is not Batel!

Bava Kama 69a (Mishnah): Tzenu'im (pious people) would take coins and say 'whatever Kerem Revai (fourth-year produce) was gathered from my field is redeemed on these coins.'

The text should say 'whatever will be gathered is redeemed.'

Maseches Shevi'is (Mishnah 7:7): If Shemitah Peros give taste to a mixture Min b'Eino Mino, one must do Bi'ur. In a mixture Min b'Mino, we are concerned for Mashehu. Any amount of Shevi'is forbids Min b'Mino, and Min b'Eino Mino, b'Nosen Ta'am.

Rishonim

Rambam (Hilchos Shemitah 7:22): The general rule is, if Shemitah Peros became mixed with other Peros, b'Mino the Shi'ur is Mashehu, and b'Eino Mino it is b'Nosen Ta'am.

Rambam (Hilchos Ma'achalos Asuros 15:8): Regarding a mixture of Shemitah Peros, Min b'Mino the Shi'ur is any amount, and Min b'Eino Mino it is b'Nosen Ta'am. However, this is not an Isur Torah. The mixture is permitted, just one must eat it with Kedushas Shemitah.

Ra'avad: There is another Bi'ur of Shemitah Peros, i.e. burning or burial, when the last species is finished in that one of the three lands for Shemitah (Yehudah, Galil and Ever ha'Yarden). At this time, whether b'Mino or b'Eino Mino, it forbids only if it gives taste.

Radvaz: The Ra'avad criticizes the Rambam for not explaining that b'Mino is b'Mashehu only before Zman Bi'ur. Since one must eat them with Kedushas Shemitah, this is like Davar she'Yesh Lo Matitrim. After Zman Bi'ur, it must be burned, and it is like other Isurei Torah. Even b'Eino Mino, it forbids b'Nosen Ta'am. R. Shimshon explained oppositely.

R. Shimshon (Shevi'is 7:7): Shevi'is forbids Mashehu Min b'Mino, i.e. after Zman Bi'ur. Before Bi'ur it has Kedushas Shemitah only if it is b'Nosen Ta'am. B'Eino Mino, even after the Bi'ur it is b'Nosen Ta'am. Nedarim 58a requires investigation, for it seems to discuss Gidulim (added growth,) and Min b'Eino Mino does not apply to this!

Migdal Oz: The Rambam wrote like it says in Nedarim and Shevi'is. The Mishnah Torah is an abbreviation of the Gemara. He does not inject Sevaros (reasoning).

Note: It seems that he means that since one could explain the Mishnah like the Ra'avad, or like R. Shimshon, the Rambam did not rule about this. I find this difficult, for in his introduction, the Rambam says that learning the Mishnah Torah will suffice to know all of Oral Torah!

Kesef Mishneh: The Rambam comes to answer why R. Yochanan and Reish Lakish did not exclude Shemitah from the rule of all Isurim, just like they excluded Tevel and Yayin Nesech, because Shemitah is not an Isur Torah.

Perush ha'Mishnayos (Avodah Zarah 5:8): All Isurei Torah forbid b'Nosen Ta'am, whether b'Mino or b'Eino Mino, except for Tevel and Yayin Nesech. Shevi'is forbids b'Mashehu Min b'Mino. This does not contradict our rule, for it is not Asur to eat, just one must eat it with Kedushas Shemitah. This is why Chachamim were stringent about it, for one may eat it in the proper time.

Lechem Mishneh (Halachah 6): The Ra'avad challenges the Rambam's rule, for Shemitah after Bi'ur is an Isur Torah, and even b'Mino it is b'Nosen Ta'am! It seems that R. Yochanan omitted Shemitah because its Isur is not uniform, i.e. it is different before and after Bi'ur.

Noda b'Yehudah (2 YD 53 DH v'Emnam): The Ra'avad comes to defend the Rambam. The Ra'avad was bothered why R. Yochanan did not exclude Shemitah after Bi'ur from the rule of all Isurim, for then it is an Isur Torah! He answered that indeed, then it is b'Nosen Ta'am even b'Mino, like other Isurim. What was the Lechem Mishneh's question? The rule is that Isurei Torah are b'Nosen Ta'am even b'Mino! However, the Rambam (Hilchos Shemitah 7:22) says that Shemitah is b'Mashehu b'Mino, and he does not distinguish before and after Bi'ur. He can explain R. Shimon's words 'I said only regarding Bi'ur. Eating depends on b'Nosen Ta'am' like the Ra'avad (who is more stringent before Bi'ur) or like R. Shimshon (who is more stringent after Bi'ur). Since the law is not uniform, R. Shimon did not mention Shemitah in his rule. The Rambam rules like Chachamim, that in both cases Min b'Mino is b'Mashehu. It seems that R. Shimshon holds that R. Shimon is more stringent after Bi'ur because the person did not (fulfill his Chiyuv to) get rid of the Peros, just like we forbid Sefichim (things that grow by themselves) due to transgressors (who plant, and claim that they grew by themselves). He does not fine Min b'Mino to be b'Mashehu, for even Yayin Nesech is not so stringent.

Perush ha'Rosh (Nedarim 58a DH Shevi'is): Shemitah is Ein Lo Matirim, for whatever grows in Shemitah requires Bi'ur. If sixth-year produce grew a little in Shemitah, it requires Bi'ur like Shemitah Peros, for the Asur growth is important and is Mevatel what was planted. Regarding eating, i.e. he brought Peros to the house and they became mixed, the Shi'ur is b'Nosen Ta'am.

Tosfos (Bava Kama 69a DH Kol): According to one version, Tzenu'im used to redeem all the Kerem Revai that poor people will pick that day. Even though they cannot redeem now what will grow later (before it is picked), perhaps the growth is Batel in the majority. Even though Davar she'Yesh Lo Matitrim (one can redeem the additional growth) is not Batel, mid'Oraisa it is Batel.

Shitah Mekubetzes (69a DH v'Chen, citing R. Yeshayah): Even though Davar she'Yesh Lo Matitrim is never Batel, here there is no other solution, therefore, it is Batel (it is like Ein Lo Matirim - PF). Alternatively, an Isur that was once by itself and became mixed is not Batel; here, the Isur was never by itself.

Poskim

Rema (YD 102:4): If any Isur was not recognized before it became mixed, it is Batel even if it is Yesh Lo Matirim.

Gra (16): Tosfos (69a DH Kol) asked that (the Tzenu'im did not redeem what grows afterwards, and it is not Batel because) it is Yesh Lo Matirim. The Rema answers this (it is Batel).

Keren Orah (Nedarim 58a DH v'Derech): Our Gemara connotes that Davar she'Yesh Lo Matitrim applies to something growing to forbid b'Mashehu. This is unlike the Rema and several Rishonim, who say that Yesh Lo Matirim does not apply to something mixed from the beginning. It seems that Shemitah regarding Bi'ur is better than Davar she'Yesh Lo Matitrim (for even now it is permitted, just one must eat it with Kedushas Shemitah before the Bi'ur). However, if so, according to Shnos Eliyahu (below), why do Chachamim say that even regarding eating it is b'Mashehu? Also, if it forbids b'Mashehu, why did the Gemara ask whether the growth forbids the Ikar? Surely it does!

Shenos Eliyahu (Shevi'is 7:7, b'Sof): The Tana taught Shemitah by itself, even though it is included in the general rule, to teach unlike R. Shimon, who says that Shemitah forbids b'Mashehu only regarding Bi'ur, but regarding eating it is b'Nosen Ta'am. Rather, Shemitah is b'Mashehu b'Mino also for eating.