Pe'ah Chapter 8, Mishnah 7. To understand this mishnah we first need to know that from the days of Chazal two types of charity funds were maintained in Israel for the poor:
The kupah (fund): The charity fund was designated for the poor of the city, those who lived there permanently. The fund supplied their weekly needs, and each person received from it the amount appropriate for him, enough to last him that week. The distribution took place every Erev Shabbos.
The tamchuy (plate): A collection plate for various foods and money, which was carried each morning from house to house throughout the city to gather food and funds. The tamchuy was designated for wandering poor people who travel from city to city and stay in a place only temporarily, and it therefore supplied only their daily needs.
The amount given to a poor person traveling from place to place:
The mishnah opens and says: "Ein pochasin le'ani ha'over mimakom lemakom mikikar b'pundyon me'arba se'in b'sela" - a poor person wandering from place to place is not given less than a loaf of bread worth a pundyon, at a time when four se'in of grain sell for a sela.
Without entering into the details of the calculation, it is enough to say that this amount represents a loaf of a quarter of a kav, which is the volume of six eggs, and that is the usual quantity for two meals. It emerges that each poor person is given a loaf sufficient for his daily needs - two meals a day.
"Lan - nosnin lo parnasas linah" - if the poor person stays overnight in the place, he is given what he needs for lodging: a bed and the bedding that goes with it.
"Shavas - nosnin lo mezon shalosh se'udos" - if he remains in the place for Shabbos, he is given food for three meals, corresponding to the number of meals eaten on Shabbos.
Who may not take from the tamchuy and from the kupah:
"Mi sheyeish lo mezon shtei se'udos - lo yitol min hatamchuy" - the tamchuy is intended for someone who has nothing to eat even for that day, and therefore someone who has food for two meals, which are that day's needs, does not take from it.
"Mi sheyeish lo mezon arba esrei se'udos - lo yitol min hakupah" - someone who has enough food for the entire week should not take even the weekly sum distributed from the kupah, since he already has a sufficient quantity for that week.
One must ask: why only fourteen meals? Seemingly there should be fifteen meals counted, because of the three Shabbos meals. The answer is that the Motza'ei Shabbos evening meal is not counted, because it is covered by seudah shelishis, so there really are only fourteen meals in the week.
How the collection and distribution are done:
The kupah, which operates on a weekly basis, is collected by two people - two gabba'im. The word 'gabba'im' comes from the term for collecting and gathering, and the original meaning of the term is collectors. The reason two people collect is that no communal or congregational position is appointed with fewer than two people, out of respect for the public.
The distribution to the poor, however, is done by three, because distributing charity and deciding who receives and what he receives are considered monetary judgments, which require three judges. The three distributors have to weigh the individual circumstances of each poor person, and therefore their number matches the number of a beis din.
That is the law of the kupah. The tamchuy, by contrast, is collected by three and distributed by three. The reason is that since the tamchuy operates on a daily basis, the distribution and the giving were done immediately after the collection, and therefore the same three people were kept on for both roles.
The Rambam explains an additional reason why the tamchuy is collected by three: the sum a person gives to the tamchuy is not a fixed amount, and it therefore requires an ongoing determination. For this reason three people are needed to serve as three judges to determine how much each person must give, unlike the kupah, where the amount is fixed in advance.
In summary: In this mishnah we learned about the two charity institutions of the city - the weekly kupah for the local poor and the daily tamchuy for the poor who travel from place to place; the amount given to a poor person traveling from place to place, to one who stays overnight, and to one who remains for Shabbos; the amount a person may possess that exempts him from taking from the tamchuy (food for two meals) and from the kupah (food for fourteen meals); and the manner of collection and distribution - the kupah is collected by two and distributed by three, while the tamchuy is both collected and distributed by three.