In the previous mishnayos we explained that although the points at which produce becomes obligated in maaser are gemar melachah (the completion of its processing) and bringing the produce into the house, there are acts on the part of the person - chief among them selling the produce - that obligate the produce in maaser already at that stage, even before it has reached gemar melachah. After gemar melachah all agree that a sale creates an obligation to tithe before eating, even a casual eating (achilas arai); before gemar melachah Rabbi Meir and Rabbi Yehudah disagree: according to Rabbi Meir the sale obligates in maaser even before achilas arai, while according to Rabbi Yehudah, and this is the halachah, the sale does not obligate, and achilas arai remains permitted to the buyer until he brings the produce into his house.
Payment in Labor Instead of Money:
Our mishnah continues with the same topic, except that now it deals with a purchase whose payment is not money or property but services. A person can work and receive payment, saying: "I will work for you in exchange for figs" - he is supplying labor that serves as payment for the figs, and this is considered a sale. Under ordinary circumstances there is no difference between paying with money and paying with services.
The Worker's Right to Eat From the Produce:
But there is a separate matter to take into account: the Torah establishes that anyone who works with produce before gemar melachah is entitled to eat from it whenever he wishes, and this has nothing to do with maaser or with anything else. A similar halachah, perhaps a more familiar one, was stated regarding an animal: one who uses an animal to thresh wheat may not muzzle it, and must allow it to eat from the food as it pleases. The same applies to people: workers who work with produce that has not reached gemar melachah may likewise eat from it while they work, and this is a leniency granted by the Torah itself.
Accordingly, when a worker works in exchange for food, his labor would seemingly be considered payment for the food, and this would advance his obligation in maaser. But since the Torah permits him to eat from the produce while he works in any case, the food is not considered part of his wages. And even if he stipulated in the agreement, "I am working in exchange for being able to eat from the produce as well" - such a condition has no substance, for the Torah has already granted him the right to eat. Therefore this worker is not considered to have paid for the food, and he may go on eating achilas arai by virtue of his entitlement from the Torah.
The Mishnah's Ruling in Practice:
One who hires a worker for the job of drying figs - whether his task is to lay them out to dry on the roof or to cut off their stems - this is work performed before gemar melachah. Seemingly there would be room here to enter into the dispute of Rabbi Meir and Rabbi Yehudah regarding a sale, but this is not a sale at all, since the Torah has already granted the worker the right to eat from this produce before its processing is complete. And even if the worker stipulated "on condition that I may eat from the figs I am working with" - this accomplishes nothing, since he is permitted in any case. He may eat and he is exempt from any obligation of maaser, because this is not a sale to him but rather the Torah's gift to him at the time of his work.
By contrast, if the worker stipulated: "I will work with your figs to spread them out on the roof on condition that I and the members of my household may eat" - with regard to himself this is not a sale, since the Torah granted him the right to eat; but the figs given to his son are payment rendered for his labor, and that is a full-fledged sale. Therefore, even though this takes place before gemar melachah, the figs that the son eats are obligated in maaser.
The same law applies whether he stipulated "on condition that I and my sons may eat" or "in exchange for my labor my son shall eat from the figs":
The worker himself: he eats and is exempt from maaser, because the Torah granted him the right to eat.
His son: he must tithe the food before eating it, even though this takes place before gemar melachah, since this is a sale - and this follows the view of Rabbi Meir, that a sale obligates in maaser even before gemar melachah and before the eating.
If the worker stipulated: "on condition that I may eat from the figs both while I am setting them out to dry and afterward" - while he is laying the figs on the roof he eats and is exempt from maaser, since this is part of the Torah's permission for a worker to eat in the course of his work. But once the produce has been set out to dry, his eating is not by virtue of the Torah's permission but by virtue of the contract he entered into; it turns out that he is receiving his wages and is like one who paid for them with his labor, and this is a sale. He is therefore obligated to tithe, and not only according to Rabbi Meir but according to all opinions, since this is after the work has been completed. A worker who eats after the produce has been set out to dry - his eating is by virtue of his contract and not by virtue of the leniency the Torah granted him.
"Zeh haklal" - this is the rule: one who eats by virtue of the right the Torah granted him is exempt from tithes. One who eats not by virtue of that right but by virtue of an agreement he entered into is in effect purchasing his food with his labor, and he is obligated to tithe: according to Rabbi Meir even before the work is completed, and according to all opinions once the work is completed.