This mishnah continues the discussion of the line between casual eating and a fixed meal, this time regarding drinking wine straight from the winepress. The familiar rule is that produce and liquids that have reached the completion of their processing may not be eaten as a fixed meal before tithes have been separated, while casual eating is permitted. The question before us: when is drinking from the wine in the press considered casual, and when does it take on the character of a fixed consumption that obligates tithing.
Two introductory points about how wine was drunk in the days of the Mishnah:
Wine is not a casual drink: People do not sip wine offhandedly; drinking it is an act with a formal character. Even today a person does not grab a bottle of wine for a quick swig. It follows that the very fact that we are dealing with wine may lend the drinking the character of a fixed consumption.
Diluting the wine with water: In the time of the Mishnah wine was preferably drunk mixed with water, and there is an opinion that wine that has not been mixed with water never even attains its superior status. Adding the water is a formal preparation of the drink for consumption, and it too suggests a consumption that is not casual.
The water mixed into the wine was sometimes cold and sometimes hot - a sort of hot wine drink - and the mishnah discusses both of these possibilities.
The wording of the mishnah:
The mishnah opens: "shoteh al hagat" - a person may drink from the wine in the pit in the ground. The phrase "over the press" is meant literally: the drinker's head and most of his body are actually positioned above the press. As long as he drinks right at the press, his drinking is casual; but once he moves away from the press and drinks elsewhere, the consumption becomes formal and obligates tithing, and certainly when he adds water to make the wine fit for drinking.
According to Rabbi Meir, one who drinks over the press is exempt from tithing "bein bechamin bein betzonen" - it makes no difference whether he mixed the wine with hot water or with cold, since he has placed his body directly over the press and his drinking is casual drinking.
The opinion of Rabbi Eliezer ben Tzadok:
Rabbi Eliezer ben Tzadok obligates even in this case: there is no permission to drink even directly over the press without separating tithes. Two explanations are given for this:
According to the Bartenura: The concern is that the person may shift his body away from the press and find himself drinking at a distance from it, and wine mixed with water that is drunk away from the press is a complete consumption from which there is no way back.
According to Rashi (in Eruvin): The problem does not depend on moving the body away at all; rather, the very mixing of water into the wine turns the drinking into a formal consumption that obligates tithing.
The opinion of the Sages - and this is the halachah:
The Sages draw a distinction: "bechamin chayav uvetzonen patur". The reasoning is close to that of Rabbi Eliezer in the previous mishnah - that a person does not pour leftover hot wine back into the press, since it would ruin the wine in the pit. Since there is no way back, he is holding a small, separate batch of mixed wine, and since it stands on its own as something that has reached the completion of its processing, he must separate tithes from it before drinking.
But with cold water, when he drinks directly over the vat, if any wine were left in his hand he would simply pour it back into the pit. Therefore there is no separate, distinguishable batch here, and the drinking remains a casual eating that is exempt from tithes. The halachah follows the Sages.
In summary: The principle that emerges from the mishnah is that as long as the liquid has not reached a stage of permanence and separation, one may drink from it casually without separating tithes. One who drinks over the vat itself, with his head and most of his body there, is drinking casually; but actions that give the liquid the character of a separate, irreversible batch - such as mixing it with hot water, according to the Sages - fix it and obligate it in tithes.