Ohalos, Chapter 18, Mishnah 1. A beis hapras is a field in which a grave was plowed over, so that crushed bone may be scattered anywhere within it. Its tumah is not min haTorah at all: it is a rabbinic decree. Our mishnah asks a very practical question about such a field: if a vineyard is standing in a beis hapras, how do the workers get the grapes out and bring them to the winepress without the grapes becoming tamei? To follow the mishnah's answer, we first need a second rabbinic decree, and then a principle about what happens when two rabbinic decrees meet.
Hechsher: how food becomes able to receive tumah
By Torah law, produce is immune to tumah until two conditions have been met. The first is separation: it must be plucked, cut, or otherwise removed from whatever it was growing on, whether soil or branch. The second is contact with liquid, and not just any liquid, but one of the shiva mashkin, the seven that bring about hechsher. They are remembered by the familiar mnemonic yad shachat dam: yud for yayin (wine), daled for d'vash (honey); then in shachat, shin for shemen (oil), ches for chalav (milk), tes for tal (dew); and in dam, daled for dam (blood) and the closing mem for mayim (water). Fruit that has never met one of these seven, even after it has been picked, stays outside the system entirely: bring it up against tumah and nothing occurs, because it has no capacity to absorb tumah in the first place.
Chazal, however, added a decree here, and it is one of the famous eighteen enactments recorded in Maseches Shabbos. Grapes that a person intends to bring to the winepress to be pressed for wine, as opposed to grapes he plans to take to the market and sell as grapes, are treated as though they had already been wetted from the moment they leave the vine. Even though to the eye they are perfectly dry, they are considered hechshered and capable of receiving tumah.
What prompted such a ruling? Several explanations are offered, and one of them is drawn from ordinary vineyard practice. Wine grapes are sensitive, and judging the precise day for the harvest is a matter of skill. An owner would go up and down the rows pressing individual grapes between his fingers to gauge their ripeness and the quality of the juice they released. That is not yet wine, but it is moisture, and it ends up sitting on the fruit. Because the habit was so widespread, Chazal issued a blanket rule: any grapes designated for the press are regarded as having received their liquid already at the moment of picking.
Two decrees together
Now we have two rabbinic institutions in front of us. The tumah of a beis hapras is d'rabbanan: min haTorah a person walking there is not tamei. And the hechsher of dry grapes is d'rabbanan: min haTorah those grapes never touched a liquid and cannot receive tumah at all. And here is the key: Chazal were lenient where two rabbinic decrees have to be stacked on each other.
So we are holding two rabbinic creations at once. First, the tumah of a beis hapras: by Torah law someone who walks across that field carries nothing at all. Second, the hechsher of dry grapes: by Torah law fruit that never met one of the seven liquids has no ability to absorb tumah whatsoever. And the decisive principle is this: where a ruling would require one rabbinic stringency to be built upon another, Chazal chose the lenient path.
The mishnah's procedure according to Beis Hillel
The mishnah opens: "Keitzad botzrim beis hapras" - how does one harvest a vineyard that is a beis hapras? The word btzirah is specifically the harvesting of grapes; botzrim are grape pickers, just as moskim are those who gather olives. The question is exactly how they should go about it so that the grapes do not become tamei.
The opening requirement concerns the workers themselves. They have to be free of every tumah other than the one the field itself imposes. Standing in a beis hapras does render a man tamei by rabbinic law, and that much has already been factored in; but he may not be carrying any additional tumah on top of it. Hence "mazim al ha'adam ve'al hakeilim": the harvester and the utensils he will work with are sprinkled with the purifying waters prepared from Parah Adumah ash, on the third day, and "v'shonim," the sprinkling is done a second time on the seventh, following the standard sequence of taharah. At that point he is tahor as far as Torah law is concerned, and he may proceed.
"U'botzrim u'motzi'im chutz labeis hapras": they harvest the grapes and carry them out of the beis hapras. Technically we could have objected: the man is standing in a beis hapras and is tamei, and the grapes are automatically hechshered to receive tumah the instant they are picked, since that is the special rule for wine grapes. But both of those are only rabbinic, so it is fine. Pick them and move them out.
Once the grapes leave the field, however, the same workers may not continue with them. "V'acheirim m'kablim meihen u'molichim lagas": specifically others, people who never entered the beis hapras and never contracted its tumah, take the grapes from them and bring them to the winepress. The pickers themselves must stay away from the gas, because at the press there is wine. There the grapes really are wet, and contact with tumah would make them tamei min haTorah. That is no longer a rabbinic decree resting on a rabbinic decree, and so the men who were in the beis hapras must not be handling the fruit at that stage.
At the moment of the handover, the two groups have to be careful not to touch one another. A person who became tamei in a beis hapras has the status of one who is tamei from a meis, an avi avos hatumah, and he conveys tumah to people and to vessels. Hence the mishnah's next clause: "Im nagu eilu b'eilu, t'mei'in." If the two shifts failed to avoid direct contact and touched each other, the receivers are now tamei, having touched the pickers, and they may no longer carry the grapes to the gas. As long as they kept apart, the arrangement works.
Is this the view of all? The mishnah concludes this section "k'divrei Beis Hillel": this is the position of Beis Hillel, who hold that Chazal were lenient here because both the tumah of a beis hapras and the automatic hechsher of the grapes are rabbinic.
Beis Shammai's stricter procedure
"Beis Shammai omrim." Beis Shammai disagree. In their view the ordinary decree stands even in a beis hapras: grapes picked for the press are hechshered to receive tumah, even though the only tumah in sight is the rabbinic tumah of the field. Consequently, if the pickers touch the grapes, the grapes become tamei. If you want to harvest b'taharah and bring the fruit to the winepress, the picker must not touch the grapes at all, and in truth he may not even touch the magal, the curved sickle used for cutting the clusters, since the magal would become tamei from him and would pass that tumah on to the grapes.
What can he do? "Ochez es hamagal b'siv": he holds the sickle by way of siv, the fibrous material that grows around the trunk of a palm tree, wrapping the handle in it rather than grasping it directly. Why specifically the siv of a date palm and nothing else? Because siv is not m'kabel tumah, so his hand's tumah stops there and never reaches the blade.
"O" - the mishnah offers an alternative: "botzeir b'tzar." What is a tzor? The term shows up in Chumash Shemos, in the account of Moshe Rabbeinu's travels after he parted from Yisro, where the posuk (4:25) relates that Tzipporah took a tzor and performed bris milah on her son. A tzor, then, is a stone that has been given a sharp edge. So the clusters may be severed with such a stone, since stone has no susceptibility to tumah; the Bartenura notes that it does not even carry the status of a kli.
And after the clusters are cut, where do they land? "V'nosein l'soch hak'fishah": into the sort of basket used in olive production. One might object that such a basket is itself capable of receiving tumah. The resolution lies in its size: these were enormous baskets, and any vessel whose capacity reaches forty se'ah of liquid is beyond the reach of tumah, which is precisely the dimension of the baskets employed at the olive press.
"U'molich lagas": he himself may then bring the basket to the winepress, and he does not need to hand it over to anyone else. Might he forget himself along the way and touch the grapes? We are not concerned, because the grapes are lying in a k'fishah, an olive basket rather than the usual grape basket, and that unusual sight will keep reminding him that special care is needed here.
Rebbi Yosi: when do these leniencies apply?
"Omer Rebbi Yosi: Bameh devarim amurim?" Rebbi Yosi asks when all these arrangements are available: according to Beis Hillel, cutting normally and passing the fruit to a second team at the edge of the field, and according to Beis Shammai, the wrapped sickle or the stone together with the oversized basket. Either way, both schools are supplying a workable path.
His qualification is contained in the words "b'kerem hane'eseh beis hapras." The concessions were designed for a case where the vines were already growing and only later did the field acquire the status of a beis hapras. "Aval hanotei'a beis hapras" - the picture changes when a man knowingly plants his vineyard in ground that already carries that status, and defends himself by pointing out that he studied a mishnah in Maseches Ohalos and knows there are ways around the problem. Such a person is penalized. "Yimacher lashuk": his only option is to gather the fruit and sell it in the marketplace as grapes, perhaps for a mishloach manos tray or a Chamishah Asar B'Shevat basket, but never for the press, because grapes intended for wine are hechshered on their own even with no liquid ever touching them. Where the vineyard predates the problem we look for a way to spare him the loss of his wine production; where he walked into the situation deliberately, we do not.
The Tiferes Yisrael raises the obvious difficulty: if a workable method exists, why should planting there in the first place be objectionable at all? His answer is that what troubles Rebbi Yosi is the affront to the deceased, bizayon hameis. Once a person is aware that a grave lies beneath that soil, he does not go and set out vines over it.
The Bartenura, though, records that we do not follow Rebbi Yosi in practice. The mishnah's arrangements are available across the board. For Beis Hillel it suffices that the workers be free of Torah-level tumah by means of the sprinklings on day three and day seven; they cut the fruit, bring it beyond the boundary of the field, and transfer it to a different group who take it onward to the press, since we keep anyone who was inside the beis hapras away from the wine itself, where the fruit could pick up tumah on a Torah level. Beis Shammai demand more: the harvesters may have no contact with the grapes, so they grip the sickle through siv, which is impervious to tumah, or else cut with a stone, and they deposit the clusters in the oversized olive-press baskets, whose capacity puts them beyond tumah. In return, Beis Shammai grant a concession of their own: no second crew is needed, since the strange sight of that basket serves as a standing reminder to keep his hands off the fruit. And because Rebbi Yosi's limitation is not the accepted ruling, these methods are equally available whether the vines were there before the field became a beis hapras or whether the man planted them there knowing full well what the ground was.