יורה דעה רי״דYoreh De'ah 214

Se’if 1א׳

דְּבָרִים הַמֻּתָּרִים וְהַיּוֹדְעִים בָּהֶם שֶׁהֵם מֻתָּרִים נָהֲגוּ בָּהֶם אִסוּר, הָוֵי כְּאִלּוּ קִבְּלוּ עֲלֵיהֶם בְּנֶדֶר וְאָסוּר לְהַתִּירָם בָּהֶם. הִלְכָּךְ, מִי שֶׁרָגִיל לְהִתְעַנּוֹת תַּעֲנִיּוֹת שֶׁלִּפְנֵי רֹאשׁ הַשָּׁנָה וְשֶׁבֵּין רֹאשׁ הַשָּׁנָה לְיוֹם כִּפּוּרִים, וּמִי שֶׁרָגִיל שֶׁלֹּא לֶאֱכֹל בָּשָׂר וְשֶׁלֹּא לִשְׁתּוֹת יַיִן מֵרֹאשׁ חֹדֶשׁ אָב אוֹ מִי"ז בְּתַמּוּז, וְרוֹצֶה לַחֲזֹר בּוֹ מֵחֲמַת שֶׁאֵינוֹ בָּרִיא, צָרִיךְ ג' שֶׁיַּתִּירוּ לוֹ. אִם בְּשָׁעָה שֶׁהִתְחִיל לִנְהֹג הָיָה דַּעְתּוֹ לִנְהֹג כֵּן לְעוֹלָם, וְנָהַג כֵּן אֲפִלּוּ פַּעַם אַחַת, צָרִיךְ הַתָּרָה וְיִפְתַּח בַּחֲרָטָה שֶׁמִּתְחָרֵט שֶׁנָּהַג כֵּן לְשֵׁם נֶדֶר. לְפִיכָךְ, הָרוֹצֶה לִנְהֹג בִּקְצָת דְּבָרִים הַמֻּתָּרִים, לִסְיָג וּפְרִישׁוּת, יֹאמַר בִּתְחִלַּת הַנְהָגָתוֹ שֶׁאֵינוֹ מְקַבֵּל עָלָיו כֵּן בְּנֶדֶר, וְגַם יֹאמַר שֶׁאֵין בְּדַעְתּוֹ לִנְהֹג כֵּן אֶלָּא בַּפַּעַם הַהוּא אוֹ בַּפְּעָמִים שֶׁיִּרְצֶה, וְלֹא לְעוֹלָם. אֲבָל הַנּוֹהֲגִים אִסוּר בִּדְבָרִים הַמֻּתָּרִים מֵחֲמַת שֶׁסוֹבְרִים שֶׁהֵם אֲסוּרִים, לֹא הָוֵי כְּאִלּוּ קִבְּלוּם בְּנֶדֶר. וְיֵשׁ מִי שֶׁאוֹמֵר, שֶׁאִם טוֹעֶה וְנָהַג אִסוּר בְּדָבָר הַמֻּתָּר, נִשְׁאָל וּמַתִּירִים לוֹ בִּשְׁלֹשָׁה כְּעֵין הַתָּרַת נְדָרִים. וְאִם יוֹדֵעַ שֶׁהוּא מֻתָּר וְנָהַג בּוֹ אִסוּר, אֵין מַתִּירִין לוֹ אֲפִלּוּ כְּעֵין הַתָּרַת נְדָרִים; דְּהָוֵי כְּאִלּוּ קִבְּלוֹ עַל עַצְמוֹ כְּאִסוּרִים שֶׁאֲסָרְתָן תּוֹרָה שֶׁאֵין לָהֶם הֶתֵּר לְעוֹלָם. וְהַמִּנְהָג כַּסְּבָרָא הָרִאשׁוֹנָה.

Things that are permitted, and those who know of them that they are permitted have practised a prohibition in them — it is as though they had accepted them upon themselves by a vow, and it is forbidden to permit them to them. Therefore, one who is accustomed to fast the fasts that are before Rosh Hashanah and those that are between Rosh Hashanah and the Day of Atonement, and one who is accustomed not to eat meat and not to drink wine from the New Moon of Av or from the seventeenth of Tammuz, and who wishes to retract because he is not in health, requires three to release it for him. If at the hour when he began to practise it his intention was to practise so for ever, and he practised so even one time, he requires release, and he shall open with regret — that he regrets having practised so for the sake of a vow. Therefore, one who wishes to practise some permitted things, for a fence and for abstinence, shall say at the beginning of his practice that he does not accept it upon himself by a vow; and he shall also say that it is not in his intention to practise so save on that occasion, or on the occasions that he shall wish, and not for ever. But those who practise a prohibition in permitted things because they hold that they are forbidden — it is not as though they had accepted them by a vow. And there is one who says that if he errs and practises a prohibition in a permitted thing, he asks, and they release it for him before three, after the manner of the release of vows; but if he knows that it is permitted and practised a prohibition in it, they do not release it for him even after the manner of the release of vows, for it is as though he had accepted it upon himself like the prohibitions that the Torah forbade, which have no release for ever. And the custom is in accordance with the first reasoning.

Se’if 2ב׳

קַבָּלַת הָרַבִּים חָלָה עֲלֵיהֶם וְעַל זַרְעָם; וַאֲפִלּוּ בִּדְבָרִים שֶׁלֹּא קִבְּלוּ עֲלֵיהֶם בְּנֵי הָעִיר בְּהַסְכָּמָה, אֶלָּא שֶׁנּוֹהֲגִין כֵּן מֵעַצְמָם לַעֲשׂוֹת גָּדֵר וּסְיָג לַתּוֹרָה; וְכֵן הַבָּאִים מִחוּץ לָעִיר לָדוּר שָׁם, הֲרֵי הֵם כְּאַנְשֵׁי הָעִיר וְחַיָּבִים לַעֲשׂוֹת כְּתַקָּנָתָן, וְאַף בִּדְבָרִים שֶׁהָיוּ אֲסוּרִים בָּהֶם בְּעִירָם מִפְּנֵי מִנְהָגָם וְאֵין מִנְהַג הָעִיר שֶׁבָּאוּ לָדוּר בָּהּ לֶאֱסֹר, הֻתְּרוּ בָּהֶם אִם אֵין דַּעְתָּם לַחֲזֹר.

The acceptance of the many takes effect upon them and upon their seed; and even in things that the men of the city did not accept upon themselves by an agreement, but that they practise so of themselves, to make a fence and a hedge for the Torah. And likewise those who come from outside the city to dwell there — they are as the men of the city and are bound to act according to their ordinance. And even in things in which they were forbidden in their own city by reason of their custom, where it is not the custom of the city to which they have come to dwell to forbid, they are permitted in them, if it is not their intention to return.