There is a machlokes Rishonim whether a Reshus HaRabim needs to be 16 amos wide and have 600,000 passersby or only the former. What is the custom today?
עירובין דף ו.
ת”ר כיצד מערבין דרך רשות הרבים עושה צורת הפתח מפכאן ולחי וקורה מכאן. וכתב רש”י רה”ר – משמע רחב שש עשרה אמה ועיר שמצויין בה ששים ריבוא.
What classifies as a Reshus Harabim?
Rashi explains that it requires two conditions, it needs to be less than 16 amos in width and have less than 600,000 people passing through there.
This idea that a Reshus Harabim needs 600,000 people is the opinion of many of the Rishonim, but the Rambam and other Rishonim argue and say that the single requirement is that the width of the street is less than 16 amos. The Shulchan Aruch brings both opinions.
Their disagreement is based on how far we compare it to the Midbar. For all the Melachos of Shabbos we learn from the Mishkan, and in the Mishkan the width of the path that the wagons carrying the keroshim were in total 16 amos. How we come to that calculation was discussed at length in Shabbos (Daf 99).
Now Rashi and other Rishonim take this one step further and say that since the number of people in the Midbar was 600,000, we cannot have a Reshus Harabim without this amount of people, as otherwise it would not be comparable to the Deglei HaMidbar. Tosafos (here) acknowledges that in reality there were more than 600,000 people in the Midbar, since that number does not include children, women or goyim. But since the pasuk only mentions 600,000 that is the deciding number we will measure by, as it is from the pasuk that we derive what is considered to be a Reshus Harabim.
The Eishel Avraham suggests that because Tosafos says we can only base ourselves on what is explicitly in the Torah – which does not include children, women, or goyim, perhaps when we count 600,000 to make a Reshus Harabim it too must be only Jewish men who are adults. This is not the opinion of most of the Acharonim, and we do not rely on this leniency.
About 200 years ago the Sefer Mishkanos Yaakov was published by Rabbi Yaakov Bruchin, one of the great Lithuanian gedolim. There, he wrote a famous teshuvah where he argued against the custom to rely on the leniency that we require 600,000 people. According to his understanding the only requirement is to have streets less than 16 amos wide. He argued there are more Rishonim that disagreed with Rashi than those who agreed with Rashi. He additionally writes that Rashi cannot mean that there needs to be 600,000 people passing by all the time, for that seems highly implausible. Rather it needs to be a street which can allow the passage of 600,000 people.
The Bais Ephraim who was the main proponent to argue with the Mishkanos Yaakov writes that perhaps he may be right that there are more Rishonim who do not require 600,000 people, however the minhag in Ashkenaz was always to be lenient in this matter and to rely on the opinion of Rashi that in order for it to be a Reshus Harabim it would need 600,000 people.
The Oruch Hashulchan writes that since all the cities always built an eiruv, and in most cases the streets were wider than 16 amos, it seems the custom was to rely on Rashi. He adds that it is as if a voice of heaven proclaimed that the halacha follows this opinion.
The general custom was to follow Rashi, and there have been eiruvin in cities where they definitely had wide streets such as Paris, Warsaw, and Vienna. As these eiruvin were built by the great gedolim of those times, we can assume they held that a Reshus Harabim needs 600,000 people.
The Mishna Berurah does write that one should try and be stringent, and there have been many individuals who accepted this upon themselves. They do not carry in an eiruv unless it has a narrow street or doors built at the end which would be sufficient even for a Reshus Harabim.
Rabbi Dovid Baran (one of the great tzaddikim of Yerushalayim, who died in 1946) was involved when the neighborhood Shaarei Chessed was built. He arranged that the streets should not be 16 amos wide as he followed the opinion of the Mishkanos Yaakov. His brother Rabbi Zalman Baran, who was one of the founders of Meah Shearim, also made sure the streets were built less than 16 amos wide. It is said that the way he measured it was as follows. He brought a camel which was carrying two sacks of coal, the camel would walk in the middle of the street and on either side he had two people walking. It is not clear from where this measurement comes.
One of the interesting proofs the Mishkanos Yaakov brings is from the following case. The Gemara in Shabbos (Daf 80) tells us that if one carries eye makeup even if the amount was only enough for one eye they would be liable. The Gemara asks: we learned elsewhere that the amount is for two eyes? To this Chazal answered that that was said about village women. Rashi explains that in the villages it was not required to be as modest as in the cities, for they were not exposed to city life, and therefore they had both eyes exposed. Hence why the amount to be liable is for two eyes.
Now the Mishkanos Yaakov asks the following question. It is implied in the Gemara that if a woman in a village carries makeup for two eyes on Shabbos, they would be liable. But one is only liable in a place which is considered a Reshus Harabim mid’oraysa? According to the opinion that it would need to be 16 amos wide and have 600,000 people passing through in order for it to be a Reshus Harabim, would one find these circumstances in a village? If the only requirement is that it should have wide streets, then yes one would find this easily in any village. But 600,000 people were only found in very large cities, not in any village. How was it possible for a village woman to be liable if they carry makeup for both eyes? From this Gemara, it seems to be a very strong proof to the opinion of the Rambam.
While there are ways to refute this proof and understand the case of village women differently, it is quite an ingenious proof that deserves to be mentioned. The custom was to be lenient like Rashi, but the Mishkanos Yaakov created quite a storm that shook the Torah world.