Peah chapter 7, mishnah 6. The mishnah before us deals with the law of revai. For the first three years after a tree is planted its fruit is called orlah, and it is forbidden to eat it or to derive any benefit from it. In the fourth year the fruit is called revai, and its status resembles that of Maaser Sheni: it must be brought up to Jerusalem and eaten there, or else redeemed, with the redemption money brought up to Jerusalem and spent on food to be eaten there.
The scope of the law of revai - a dispute in the Gemara:
The Gemara in Berachos (35a) records a dispute as to whether the law of revai applies to all fruit trees:
The first opinion: the law applies to all trees, and therefore the subject is called 'neta revai' - plantings in their fourth year.
The second opinion: the law applies only to grapes, that is, to vines, and therefore it is called 'kerem revai'.
Our mishnah opens with the words "kerem revai" - a fourth year vineyard. According to the opinion that the law applies only to grapes, this wording is self explanatory. But even according to the opinion that the law applies to every kind of fruit tree, the mishnah used the term "kerem" because the latter part of the mishnah deals with laws that pertain to grapes alone. The first law in the mishnah, however, applies to every kind of fruit tree.
The dispute between Beis Shammai and Beis Hillel regarding the added fifth and bi'ur:
Concerning the produce of the fourth year, Beis Shammai say: "ein lo chomesh ve'ein lo bi'ur" - it has no added fifth and it has no bi'ur. Both of these rulings were stated in order to distinguish it from Maaser Sheni:
The added fifth: one who redeems Maaser Sheni must add a fifth - an addition of twenty five percent of the original value, which amounts to a fifth of the total sum after the addition. According to Beis Shammai, this law of the added fifth does not apply to the redemption money of a fourth year vineyard.
Bi'ur: in the fourth year and in the seventh year of the shemittah cycle a person is obligated to remove from his possession all the Terumah and tithes that he has not separated and not given to those entitled to them, and to give them to the appropriate parties or destroy them. With Maaser Sheni, if it has not been eaten by the time of bi'ur, it must be removed. According to Beis Shammai, the law of bi'ur does not apply to a fourth year vineyard.
Beis Hillel disagree on both points and say: "yesh lo" - it does have them. A fourth year vineyard does carry the obligation to add a fifth upon redemption, and the law of bi'ur applies to it as well.
Peret and olelos in a fourth year vineyard:
From here the mishnah moves on to a matter that pertains to vines alone. Beis Shammai say: "yesh lo peret ve'yesh lo olelos" - it has peret and it has olelos. When a fourth year vineyard is harvested, the law of peret applies, so that the grapes which fall during the harvest belong to the poor, and so too the law of olelos, which concerns isolated clusters that have neither a shoulder nor a dangling portion, lacking the classic shape of a cluster.
The poor who acquire these grapes are required to treat them according to the laws of a fourth year vineyard: to bring them up to Jerusalem or to redeem them themselves. This is what the mishnah means when it says: "veha'aniyim podin le'atzman" - and the poor redeem them for themselves. The fruit belongs to the poor, and the task of redemption falls upon them.
Beis Hillel say: "kulo la'gas" - all of it goes to the winepress. The poor take no share in it at all. A fourth year vineyard has the same status as Maaser Sheni, which is the property of Heaven, belonging to the sanctified realm, and we merit to eat from the table of the Holy One, blessed be He. Therefore it is the owner, the farmer himself, who benefits from the fourth year vineyard - whether by eating it in Jerusalem, or by redeeming it, bringing the money up and eating from it in Jerusalem.
In summary: in this mishnah we learned the law of a fourth year vineyard and its relationship to Maaser Sheni. Beis Shammai and Beis Hillel disagree on two matters: whether the added fifth upon redemption and the law of bi'ur apply to it, which Beis Shammai deny and Beis Hillel affirm; and whether peret and olelos for the poor apply to it, where according to Beis Shammai the poor acquire the grapes and redeem them for themselves, while according to Beis Hillel "kulo la'gas", and all the fruit belongs to the owner, since it is the property of Heaven.