This Mishnah, which opens the fourth chapter of Maseches Ma'asros, deals with the acts that establish the obligation to tithe. We have already noted several times that the standard point from the Torah, from which one may no longer eat from the produce even a casual snack without tithing it, is once the work has been completed - the finishing of the processing in the field - and it has been brought into the house through the doorway, provided that it is intended for household use and not for sale. Nevertheless, we have seen that at least by rabbinic law, certain acts performed after the work is completed but before the produce is brought into the house also establish the obligation to tithe: separating Terumah Gedolah, bringing the produce into a courtyard, and the like. Our Mishnah discusses further scenarios in which the obligation is established.
The list of establishing acts, as the Bartenura enumerates it:
Ha'ur (fire) - cooking the produce over a fire.
HaMelach (salt) - salting it, spreading salt on it in order to preserve it.
HaMekach (the sale) - selling it, as we have seen above.
HaTerumah - separating Terumah Gedolah from it.
HaShabbos - Shabbos passing over it, a matter that will be explained further in this chapter.
HeChatzer (the courtyard) - bringing it into a guarded courtyard, one that provides some measure of protection, whether privacy or security, as was explained in the Mishnah in the previous chapter.
All of these, according to the Bartenura, establish the obligation to tithe even though the produce was never brought into the house, and this obligation is rabbinic.
"HaKoveish, hasholeik v'hamoleiach - chayav" - one who pickles, boils or salts is obligated:
HaKoveish - one who pickles vegetables, for example by placing them in vinegar or in salt water and the like.
HaSholeik - one who cooks the vegetables.
HaMoleiach - one who spreads salt on them in order to dry them out and preserve them.
All of these are considered, at least by rabbinic law, acts that turn the eating into a fixed meal. Once he has pickled, boiled or salted, he must tithe the produce fully before eating, and those vegetables no longer carry the allowance of eating casually.
"HaMatmin ba'adamah - patur" - one who buries produce in the ground is exempt:
One who buries vegetables in the ground, meaning so that they will ripen a bit more, is exempt. Even though this is no longer an entirely incidental act, since a certain preparation has been done to them, it is not counted among the acts that establish the eating as a fixed meal. Once he removes them from the ground, he may still eat from them in a casual manner.
"HaMetabel basadeh - patur" - one who dips his food in the field is exempt:
One who eats cucumbers or olives and the like in the field, and dips them in salt or in vinegar, is exempt. Dipping in salt is not the same as salting: salting means embedding the fruit in salt in order to pickle it, dry it out and preserve it, whereas dipping for the sake of immediate eating does not trigger the obligation to tithe, and he may eat from them right there in the field.
"HaChoveit zeisim - patur" - one who beats olives is exempt:
Olives, when eaten raw straight from the tree, are extremely bitter, and part of that bitterness comes from certain juices inside them. Beating the olive gently allows those juices to escape. The Mishnah teaches: one who beats olives so that the burning sap will come out of them has not performed an act of food preparation that turns the eating into a fixed meal, and therefore the olives are exempt from tithes.
"Hasochet zeisim al besaro - patur":
This refers to one who squeezes olives so that the oil drips directly onto his skin, to serve as a kind of ointment. Even though we said that anointing the body with olive oil is like drinking it, nevertheless squeezing it and smearing it on the skin is considered an incidental, casual use, and it is therefore exempt from tithes.
However, we saw above that the completion of the processing of olive oil takes place when it is gathered into the pit in front of the olive press. Therefore, one who makes an improvised pit - squeezing the oil and collecting it in the palm of his hand - has created a small harvest of oil that counts as a quantity in its own right, requiring tithing. This is what the Mishnah teaches: one who squeezes directly onto his skin is exempt, but one who squeezes and gathers a small pool of oil in his palm is obligated to tithe it before he anoints himself with it or drinks it, as the case may be.
The completion of processing for wine and grape juice:
For wine and grape juice, the completion of processing comes after the grapes have been trodden, when the liquid drips down and collects in the pit. One waits a few days until fermentation begins, and the sediment - the leaves and the grape skins - bubbles up and rises to the surface of the pit. Once he skims, that is, removes the floating layer on the surface of the pit, that is the completion of processing.
"Hamekapeh letavshil - patur":
One who takes wine that has not yet been clarified and puts it into a cooked dish, and removes what floats on top, is exempt. This is not a completion of processing that imposes the obligation of tithes on the wine, since the skimming was done in the dish and not in the pit, and this parallels the case of squeezing olive oil onto the skin. This refers specifically to a cold dish, for if he were cooking the grape juice or the wine over a fire, the cooking itself would establish the obligation of tithes.
"Lekedeirah - chayav, mipnei shehu k'bor katan":
On the other hand, just as we said regarding olive oil that one who gathers it into a small pool in his palm has made an improvised pit that obligates tithing, so too one who pours unfiltered grape juice into a pot: the pot becomes a small, improvised pit that collects the liquid, and therefore he is obligated. Once he has filtered off what floats on top, the requirements of tithing take effect before he may drink that wine, even for a casual, incidental drink.
In summary: In this Mishnah we learned the actions that establish the obligation of tithes once processing is complete, even before the produce has been brought home. We began with the Bartenura's list: fire, salt, sale, Terumah, Shabbos and the courtyard. And in the Mishnah itself: pickling, boiling and salting - obligated; whereas burying in the ground, dipping in the field, beating olives to release the sap and squeezing olives onto the skin - exempt. We also identified the shared principle governing oil and grape juice: whenever the liquid is gathered into a place that functions as a pit, even a small improvised pit - the palm of the hand or the pot - the obligation of tithes takes hold.