Rif Eruvin 23a {Eruvin 73a continues ... 75a}

HIDE/SHOW IMAGE
23a

{Eruvin 73a continues}
and did not participate in the shittuf in the alleyway, they are permitted in the courtyards and they are forbidden in the alleyway.

{Eruvin 73b}
If they participated in the shittuf in the alleyway, they are permitted here and here.

If they made an eruv in the courtyards and they participated in the shittuf in the alleyway, and one of the people of the courtyard forgot and did not make and eruv, they are permitted here and here.

If he is of the people of the mavoy, and he forgot and did not participate in the shittuf, they are permitted in the courtyards and they are prohibited in the alleyway, for the alleyway is to the courtyards as the courtyards as the courtyard is to the houses.

Gemara:
Our Mishna is entirely Rabbi Meir, who said that we need an eruv and need a shittuf. And for what reason did Rabbi Meir say that we need an eruv and need a shittuf? In order that the law of eruv is not forgotten among the children.

And here, since most do make an eruv, the concept of eruv will not be lost from them.

Rav Yehuda said: Rav did not read in the Mishna "open one to the other."
What is the reason?
For Rav holds that an alleyway may not be permitted via a lechi or korah until it has houses and courtyards {=plural courtyards} opening into it, and these {courtyards}, since they are open one to the other, are reckoned to be one courtyard.

Gufa: {to return to the main text}
Rav said: alleyway may not be permitted via a lechi or korah until it has houses and courtyardsopening into it.
{Eruvin 74a}
And Shmuel said: Even one house and one courtyard.
And Rabbi Yochanan said: Even a ruin.

And we establish like Rav, firstly because Shmuel retracted to Rav in the matter of a certain alleyway in which Avin bar Ihi resided, and so Rabbi Yochanan is one against two. And our Mishna also support him {=Rav}, for it states that the alleyway is to courtyards as courtyards are to houses. And furthermore, Rav Nachman said in the first perek {5a}: The alleyway is not permitted via a lechi or korah unless its length is greater than its width, and until there are houses and courtyards opened into it.

{Eruvin 74b}
Rav Yehuda cited Rav: An alleyway in which {=a courtyard and house on} one side was occupied by a gentile and the other side was occupied by an Israelite, we may not make an eruv there by way of windows {on only one side of the alleyway} {Eruvin 75a} for it is forbidden to live alone with an idolator.

{This is one possible interpretation of the configuration. The Israelites's houses are connected via windows, and the gentile lives on the other side of the alleyway.}

Mishna:
Two courtyards, one farther in than the other,