אורח חיים ת״הOrach Chayim 405

Se’if 4ד׳

מִי שֶׁיָּצָא חוּץ לַתְּחוּם שֶׁלֹּא לָדַעַת, מֻתָּר לַעֲשׂוֹת לוֹ מְחִצָּה שֶׁל בְּנֵי אָדָם שֶׁעֵרְבוּ לְאוֹתוֹ רוּחַ וִיכוֹלִים לֵילֵךְ שָׁם וְיַעֲשׂוּ סְבִיבָיו כְּמוֹ מְחִצָּה וְיִכָּנֵס בֵּינֵיהֶם; וְהוּא שֶׁלֹּא יָדְעוּ אוֹתָם שֶׁנַּעֲשֵׂית בָּהֶם הַמְּחִצָּה שֶׁלְּשֵׁם כָּךְ נִקְרְאוּ, אֲבָל אִם יָצָא לָדַעַת, אָסוּר.

One who leaves the barrier without knowing, it is permitted to make a divider for himself of what people made an eruv with, in that direction and they are able to walk there. And they will make around him like a divider and he will enter between them. And the one who does not know the ones who made their dividers that are called like this, but if he left knowingly, it is prohibited.

Se’if 5ה׳

מִי שֶׁהוֹצִיאוּהוּ חוּץ לַתְּחוּם עַכּוּ"ם, אוֹ רוּחַ רָעָה אוֹ שְׁאָר כָּל אֹנֶס, אוֹ שֶׁשָּׁגַג וְיָצָא, אֵין לוֹ אֶלָּא אַרְבַּע אַמּוֹת. הֶחְזִירוּהוּ לְתוֹךְ הַתְּחוּם, כְּאִלּוּ לֹא יָצָא וַהֲרֵי כָּל הָעִיר כְּאַרְבַּע אַמּוֹת כְּבַתְּחִלָּה וְחוּצָה לָהּ אַלְפַּיִם אַמָּה לְכָל רוּחַ; אֲבָל אִם חוֹזֵר לָדַעַת, אֵין לוֹ אֶלָּא אַרְבַּע אַמּוֹת. הַגָּה: וְכֵן אִם נִכְנַס לַסְּפִינָה וְיָצְאָה הַסְּפִינָה חוּץ לַתְּחוּם וְחָזְרָה לַאֲחוֹרֵיהָ לַנָּמֵל שֶׁהִפְלִיגָה מִשָּׁם, הֲרֵי הוּא כְּאִלּוּ לֹא יָצָא דַּהֲוָה לֵיהּ כְּמוֹ שֶׁהוֹצִיאוּהוּ עַכּוּ"ם וְהֶחְזִירוּהוּ, (אוֹר זָרוּעַ).

The one that was taken out of the Shabbat barrier by non-Jews or a bad spirit or other unwilling [removals] or by accident, and he left, he only has four amot. They return him within the barrier, it is like he did not leave, and the whole city is like four amot like at first, and beyond that two thousand amot in every direction. But, if he returns knowingly, he only has four amot. Gloss: And if he entered a boat and the boat went out of the barrier, and returned afterwards to the port that it departed from, it is like he did not leave, because it is considered like non-Jews took him out and returned him (Or Zarua).