Why a level 4? The Shulchan Aruch of the Alter Rebbe is not a commentary on the Mechaber — it is an independent and complete Shulchan Aruch. For Chabad, the Alter Rebbe is הפוסק האחרון.
The full text of the Shulchan Aruch of the Alter Rebbe
סימן שנ"ט — דִּין רְחָבָה שֶׁאֲחוֹרֵי הַבָּתִּים — וּבוֹ ב סְעִיפִים
סעיף ארְחָבָה שֶׁאֲחוֹרֵי הַבָּתִּים יְתֵרָה עַל בֵּית סָאתַיִם וְלֹא הֻקְּפָה לְדִירָה…
דִּין רְחָבָה שֶׁאֲחוֹרֵי הַבָּתִּים וּבוֹ ב' סְעִיפִים:
רְחָבָה שֶׁאֲחוֹרֵי הַבָּתִּים יְתֵרָה עַל בֵּית סָאתַיִם וְלֹא הֻקְּפָה לְדִירָה, אֵין מְטַלְטְלִין בָּהּ אֶלָּא בְּד' אַמּוֹת, כְּדִין קַרְפֵּף שֶׁלֹּא הֻקַּף לְדִירָה. אֲבָל אִם אֵין בָּהּ אֶלָּא בֵּית סָאתַיִם, אֵין לָהּ דִּין קַרְפֵּף, וּמֻתָּר לְטַלְטֵל מִתּוֹכָהּ לַבַּיִת וּמִבַּיִת לְתוֹכָהּ, לְפִי שֶׁאֵינָהּ רְשׁוּת מְחֻלֶּקֶת מִן הַבַּיִת כְּמוֹ קַרְפֵּף, אַף עַל פִּי שֶׁלֹּא הֻקְּפָה לְדִירָה:
Law of the rechava (open ground) behind the houses, in 2 seifim:
A rechava behind the houses larger than beis sa'asayim that was not enclosed for dwelling (hukkaf le-dirah) — one may carry within it only within 4 amos, as the law of a karpef not enclosed for dwelling. But if it contains only beis sa'asayim, it does not have the status of a karpef, and one may carry from it into the house and from the house into it, since it is not a separate domain from the house like a karpef, even though it was not enclosed for dwelling.
סעיף בוְאִם פָּתַח בָּהּ פֶּתַח מִבֵּיתוֹ וְאַחַר כָּךְ הִקִּיפָה…
וְאִם פָּתַח בָּהּ פֶּתַח מִבֵּיתוֹ וְאַחַר כָּךְ הִקִּיפָה, אֲפִלּוּ אִם יֵשׁ שָׁם גֹּרֶן בֵּינָהּ לַבַּיִת — אֵין אוֹמְרִים שֶׁבִּשְׁבִיל הַגֹּרֶן הוּא שֶׁנִּפְתַּח פֶּתַח זֶה וְאֵין כַּאן פֶּתַח לִרְחָבָה, אֶלָּא סְתָמָא נִפְתַּח לָרְחָבָה וַהֲרֵי הִיא מֻקֶּפֶת לְדִירָה, וּמֻתָּר לְטַלְטֵל בְּכֻלָּה אֲפִלּוּ הִיא יוֹתֵר מִבֵּית סָאתַיִם.
וּמַה שֶּׁאֵין אָנוּ נִזְהָרִים מִלְּטַלְטֵל בַּחֲצֵרוֹת שֶׁאֲחוֹרֵי הַבָּתִּים — מִשּׁוּם שֶׁבִּזְמַן הַזֶּה סְתָמָן מֻקֶּפֶת לְדִירָה, כְּמוֹ שֶׁנִּתְבָּאֵר בְּסִמָּן שנ"ח גַּבֵּי קַרְפֵּף:
And if one first opened an entrance from his house to the rechava and afterwards enclosed it — even if there is a granary (goren) between them — we do not say that the entrance was opened for the sake of the granary and that there is no opening to the rechava; rather, by default the opening is to the rechava, and it thereby becomes hukkaf le-dirah, and one may carry throughout it, even if it is larger than beis sa'asayim. And the reason we are not careful about carrying in courtyards behind houses is that nowadays they are by default enclosed for dwelling, as explained in siman 358 regarding the karpef.
The Rav's special chiddushim
חידוש א — 5000-amos² limit (359:1-2)
Chiddush 1 — 5000-amos² limit (359:1-2)
Threshold beyond which not reshus hayachid
Classical position: —
The Rav's chiddush: the Alter Rebbe articulates: beyond 5000 amos² without explicit enclosure for dwelling, the space is not reshus hayachid even when fenced.
Practical consequence: tool: for large lots, eruv is required.
The Rebbe's sichos, ma'amarim and igros
⚠ Honest note: Siman שנ"ט is cited in several sichos and igros of the Rebbe. References should be validated against the physical Kehot volumes. The most direct source remains שערי הלכה ומנהג.
Practical Chabad halacha
For the Chabad chassid — Siman שנ"ט
- ① Large space (>5000 amos²) fenced without dwelling = not reshus hayachid. Reference: Shulchan Aruch HaRav 359:1-2.
⚠ For any concrete question: consult your Rav.