Chapter 2, Mishnah 2 - a Mishnah similar in subject to the previous one. The underlying principle: if an untithed fig is given to a person and he brings it into his house, he must tithe it before eating it; but if he brings it into someone else's house, he may still eat from it as a casual snack without tithing. It is a person's own house that creates the fixed obligation to tithe before eating, while his friend's house does not create this obligation.
Two places that are not the house itself:
Our Mishnah deals with two situations that are not literally the house, but places that serve as its substitute with respect to their owner:
The shop - a person's own shop, and it need not specifically be a fig shop; even if he sells other products there and happens to have figs from his field, the shop is his private domain and functions as an extension of his house.
The gateway - the entrance to the courtyard, to a person's private domain.
The case before us: two people are sitting together, one the owner of the figs and the other his guest, at the gateway of the fig owner's courtyard or in front of his shop. The owner of the figs says to his friend: "Take some of my figs".
The one who receives the figs may eat them, since the figs never reached his house and no obligation to tithe ever took hold on them on his account - he is therefore exempt from tithing. After all, he received the fig before it entered a domain of his own.
The owner of the figs, by contrast, is holding them while standing at the gateway of his courtyard or in front of his shop, and these places are his private domain and serve as a substitute for the house. It turns out that he himself is already "at home", and therefore he must tithe the figs before eating them.
This, then, is the point: both of them are eating the very same figs, and in the very same gateway, and nevertheless the giver must tithe, since his fig has already reached his house, while the recipient is exempt, since the fig became his before it reached his own house. Everything depends on the house of each individual, and this place is not the recipient's house.
The view of Rabbi Yehudah:
Rabbi Yehudah disagrees. In principle he accepts the underlying idea, but in his view one cannot call the courtyard gateway or the front of the shop a "house", because a person - at least in the era of the Mishnah - feels great discomfort and is embarrassed to eat in public view. Since that is so, this place is not yet considered a house, and therefore even the owner of the figs is exempt from tithing them, and his eating is considered a casual snack and not a fixed meal.
There are two exceptional situations in which even Rabbi Yehudah agrees that the person is considered to have the figs in his domain and must tithe them before eating:
One who turns his face away - so that people will not see him eating, for now he has privacy.
One who changes his place - moving out of public view.
In summary: In this Mishnah we learned that a shop and a gateway serve as a substitute for a house only with regard to their owners. Therefore, someone who gives figs to his fellow at the entrance of his gateway or in front of his shop must tithe them before eating, while the recipient is exempt, since the figs became his before they reached his own house. Rabbi Yehudah disagrees and holds that this is not considered the place of a house at all, since a person is embarrassed to eat in public, and in his view even the giver is exempt - unless he turned his face away or moved to another spot and removed himself from the public eye, in which case he must tithe before eating.