Eiruvin 8:1-2

Eiruvin 8:1

Here’s how one person includes others in eiruvei techumin (to shift their Shabbos boundary): he places the barrel of food and states that it is intended for any residents of his city who may need to travel on Shabbos in order to console mourners or to rejoice with newlyweds (i.e., for the purpose of a mitzvah). Anyone who accepts the terms of the eiruv before Shabbos may rely on it. After Shabbos begins is too late: an eiruv may only be made before Shabbos.

Eiruvin 8:2

The volume of food needed for an eiruv techumin is enough for two meals for each person participating. Rabbi Meir says this is based on how much one eats on weekdays and Rabbi Yehuda says it’s based on how much one eats on Shabbos, though each one intends to be lenient. (Rabbi Meir feels that one eats more at a Shabbos meal because it includes delicacies, while Rabbi Yehuda feels that one eats less at a Shabbos meal because there are more meals on Shabbos.) Rabbi Yochanan ben Beroka says that the bread for an eiruv is from a loaf that costs a pundyon when flour sells for four seah at a sela. (Translating the Mishnaic currency and measurements, this is a loaf made from 6 eggs’ volume of flour – this could be anywhere from 11 to 20 ounces of flour depending on the authority whose opinion one follows.) Rabbi Shimon says it must be two-thirds of a loaf when three loaves are baked from one kav of flour (i.e., the volume of 5.3 eggs, a little smaller than the opinion of Rabbi Yochanan ben Beroka. Remaining in a house infected with tzaraas long enough to eat a loaf half this size is sufficient to convey ritual impurity on one’s clothes; eating an unclean loaf one-quarter this size renders one ritually unclean.