סימן עד סעיף ג
הֵיכָא דְּמֻתָּר לְהַפְלִיג בַּסְּפִינָה בְּעֶרֶב שַׁבָּת, אִם נִכְנַס בָּה בְּעֶרֶב שַׁבָּת וְיָשַׁב שָׁם עַד חֲשֵׁכָה, אַף עַל פִּי שֶׁחָזַר לְבֵיתוֹ וְלָן בְּבֵיתוֹ, מֻתָּר לִכָּנֵס בָּהּ אַחַר כָּךְ בְּיוֹם הַשַׁבָּת, וּבִלְבַד שֶׁלֹּא תֵלֵךְ הַסְּפִינָה בִּשְׁבִיל יִשְׂרְאֵלִים לְחוּד. אַךְ מֵאַחַר שֶׁהָיָה בְּבֵיתוֹ בַּשַׁבָּת, קָנָה שְׁבִיתָה בְּבֵיתוֹ, וְלָכֵן אִם הָלְכָה הַסְּפִינָה יוֹתֵר מִתְּחוּם שַׁבָּת וּבָאָה בְּשַׁבָּת לַיַּבָּשָׁה, אֵין לוֹ שָׁם אֶלָּא דּ' אַמּוֹת, וְיוֹתֵר מִזֶּה אָסוּר לוֹ לָלֶכֶת שָׁמָּה. וְעַיֵּן לְקַמָּן סִימָן צ"ה.
(In cases) where it is permitted to board ship on Friday, and you boarded the ship on Friday and remained there until dark, even though you went home and remained overnight at home, you are permitted back on board ship on Shabbos,5It will not appear as though you are setting out to travel on Shabbos, but rather as though you are going into your house [Magein Avraham]. provided the ship does not make the trip exclusively for Jewish passengers. However, since you were in your house on Shabbos, you established shevisah [residence] in your house,6Shevisah refers to your residence on that Shabbos. Your place of shevisah is the focal point of your boundaries [techum]. The city in which you reside is your place of shevisah. Your techum is described in chapter 95. If you leave your place of shevisah on Shabbos, you must remain within four amohs of your point of exit. therefore, if the boat sails more than the techum Shabbos and reached land on Shabbos, you are permitted to walk only four amohs, but it is forbidden to walk more than that from the landing.7But on the boat itself there are no restrictions, as long as you boarded before Shabbos. However, if you boarded on Shabbos you may only walk four cubits even on the boat [Magein Avraham 248: 11]. See chapter 95.
תנא דבי אליהו כל השונה הלכות בכל יום מובטח לו שהוא בן העולם הבא שנאמר הליכות עולם לו אל תקרי הליכות אלא הלכות (נדה ע"ג.)