Maaser Sheni, Chapter 5, Mishnah 3. This mishnah deals with a dispute between Beis Shammai and Beis Hillel about how far we expect a fourth-year vineyard - the fruit of the fourth year - to resemble Maaser Sheni: is it like Maaser Sheni in every respect, or only to a certain extent? (As has been explained, they also disagreed whether this law applies to a vineyard and grapes alone, or to the rest of the fruits of the fourth year as well.)
"Ein lo chomesh v'ein lo bi'ur":
The mishnah opens: "Kerem reva'i, Beis Shammai omrim: ein lo chomesh v'ein lo bi'ur" - regarding a fourth-year vineyard, Beis Shammai say it has no fifth and no removal. Even though a fourth-year vineyard resembles Maaser Sheni in that it must be brought up to Jerusalem and may be redeemed, we find two additional laws in Maaser Sheni, and it is about these that they disagreed:
Chomesh (a fifth) - when Maaser Sheni is redeemed, if the one redeeming it is the owner of the fruit, he must add a fifth to the redemption money.
Bi'ur (removal) - after the third year and after the sixth year of the shemittah cycle there is a process called bi'ur, in which a person must rid himself of any Maaser Sheni in his possession, as well as any other types of terumos and maasros that he has not yet taken care of, and there is also a declaration that is recited when the mitzvah of bi'ur is fulfilled.
The question is whether these laws were stated regarding Maaser Sheni alone, or whether they apply to a fourth-year vineyard as well:
Beis Shammai: "Ein lo chomesh v'ein lo bi'ur" - a fourth-year vineyard is not like Maaser Sheni: one who redeems it does not add a fifth even when the fruit is his own, and it is also not included among the things one must remove in the fourth year and in the seventh year of the shemittah cycle.
Beis Hillel: "Yesh lo" - it does have them: it has a fifth and it has removal, and in this respect it is like Maaser Sheni.
"Yesh lo peret v'yesh lo olelos":
They disagreed about something further as well: the laws of the gifts to the poor. In a vineyard in which grapes have grown, there are gifts that must be left for the poor:
Peret - grapes that fall during the harvesting, which belong to the poor.
Olelos - isolated grapes that grow not in the form of a cluster.
The question is what the status of a fourth-year vineyard is: is it subject to the laws of peret and olelos that must be given to the poor?
Beis Shammai say: "Yesh lo peret v'yesh lo olelos, v'ha'aniyim podin l'atzman" - it has peret and it has olelos, and the poor redeem them for themselves. The vineyard is subject to the laws of peret and olelos, and the poor take them. However, they cannot eat them outside Jerusalem, and therefore they must either bring them up to Jerusalem or redeem them for themselves and bring the money up to Jerusalem.
This view stems from the foundation of their position, that a fourth-year vineyard is not identical to Maaser Sheni. Maaser Sheni is mamon gavoha - it belongs to Hashem's domain and is merely given to us to eat; but a fourth-year vineyard, according to Beis Shammai, is the owner's property, and therefore it is subject to the laws of peret and olelos, and the poor are required to deal on their own with the fourth-year status of the fruit they have received.
Beis Hillel say: "Kulo lagat" - all of it goes to the winepress. The entire vineyard, including what would ordinarily have been peret and what would ordinarily have been olelos, goes to the winepress equally. There are no gifts to the poor here at all, since it is all mamon gavoha: all the fruit has the status of a fourth-year vineyard, and it must be brought up to Jerusalem or redeemed.
In summary: in this mishnah Beis Shammai and Beis Hillel disagreed about how far a fourth-year vineyard is equated with Maaser Sheni. According to Beis Shammai it has no fifth and no removal, while on the other hand it does have peret and olelos and the poor redeem them for themselves - because a fourth-year vineyard is the owner's property. According to Beis Hillel it has a fifth and it has removal, and there are no gifts to the poor in it; rather "kulo lagat" - because all the fruit is mamon gavoha, and it must be brought up to Jerusalem or redeemed.