Eiruvin 49 - 55
What Makes an Eruv Tick
When more than one house opens into a courtyard, it is forbidden to carry anything from these houses into the courtyard on Shabbos even if it is completely enclosed. This rabbinical ban is based on the similarity this situation bears to carrying from a private domain to a public one, which is forbidden by Torah Law. The shared courtyard has the appearance of a public domain, while each separate house is similar to a private one. If carrying will be done from house to courtyard, there is a concern that people will mistakenly extend this carrying into the street as well.
The Sages, therefore, insisted that an eruv chatzeiros be made. To do this, each householder contributes some bread (or the flour or money which will be used to create the bread) which is placed before Shabbos in one of the houses. This symbolically makes that house the residence of all the householders for this Shabbos. Since they are now considered as sharing the same home and courtyard, there is no longer a danger that carrying from one to the other will be confused with carrying from a private domain to a public one.
But what is the legal mechanism for each of the householders becoming a virtual partner in the house where the eruv bread is placed?
The Sage Shmuel views it as an act of acquisition by which each householder gains a share of the house through his contribution. Why did the Sages insist on bread rather than money as an instrument of transaction? Because money is not readily available on erev Shabbos, while bread is.
Another approach is taken by the Sage Rabbah who sees the eruv as an expression of residence. Since a person's mind is focused on where his food is, we consider every contributor of food as actually living in the house where this food is located.
The gemara lists several halachic ramifications of the differing views. According to Shmuel, the eruv must have the minimal monetary value of a prutah to be valid as an instrument of transaction, and a non-food item may be used. According to Rabbah - and this is the ruling of the Shulchan Aruch (Orach Chaim 366:3) - the eruv must consist of bread, because only the location of a person's meal determines what he considers his residence. And there is no need for this food to have any minimal monetary value in order to achieve this goal.
The Slow Learner
Rabbi Preida had a student to whom he had to teach the same material 400 times before the student grasped it. One day he informed his student that he would be leaving earlier than usual in order to take care of a certain mitzvah. Although Rabbi Preida still managed to teach him the day's lesson 400 times, the student failed to understand.
"What happened?" asked Rabbi Preida?
"Ever since you, my master, told me you would be leaving early," replied the disciple, "I kept thinking you were about to leave and I could not concentrate."
"Set your mind to your study," said Rabbi Preida, "and I will teach you another 400 times."
A voice from Heaven, expressing Divine pleasure with Rabbi Preida's act, made him an unusual offer:
"What do you prefer as a reward - an additional 400 years of life, or a guarantee of a place in the World to Come for you and your entire generation?"
"If it is my choice," he replied, "I prefer that I and my entire generation merit the World to Come."
Then Hashem spoke and commanded His angels:
"Give him another 400 years of life and the World to Come for him and his generation."
This touching Talmudic tale provides an important lesson in how educators should view the challenge of teaching a slow learner: A student with the tenacity to study something 400 times, and even 800 times if necessary, will achieve his goal despite his handicap, if he has a teacher with the patience to teach the same material over and over again. Such patience in transmitting Hashem's Torah to even the slowest learner gains a reward of long life in this world while the principle credit remains for the World to Come.