The Shulchan Aruch · Orach Chayim
אורח חיים תקס״טOrach Chayim 569
Siman 569 of 697 in Orach Chayim — 2 se'ifim
הלכות תעניתLaws of Fast Days· siman 569
Se’if 1א׳
יָחִיד הַמִּתְעַנֶּה עַל כָּל צָרָה, וְעָבְרָה, אוֹ עַל חוֹלֶה, וְנִתְרַפֵּא אוֹ מֵת, צָרִיךְ לְהַשְׁלִים כָּל הַתַּעֲנִיּוֹת שֶׁקִּבֵּל עָלָיו; אֲבָל צִבּוּר שֶׁמִּתְעַנִּין עַל שׁוּם דָּבָר, וְנַעֲנִין קֹדֶם חֲצוֹת, לֹא יַשְׁלִימוּ; וְאִם תַּלְמִידֵי חֲכָמִים וְרֹב צִבּוּר רוֹצִים לְהַשְׁלִים, אֵין הַיָּחִיד רַשַּׁאי לְהַפְרִישׁ עַצְמוֹ מֵהֶם.
An individual who fasts over any trouble, and it passed, or over a sick person, and he recovered or died, must complete all the fasts that he accepted upon himself; but a congregation that fasts over anything and is answered before midday does not complete the fast. And if the Torah scholars and the majority of the congregation wish to complete it, the individual is not permitted to separate himself from them.
Se’if 2ב׳
יָחִיד שֶׁמִּתְעַנֶּה עַל צָרָה וְנוֹדַע שֶׁקֹּדֶם קַבָּלַת הַתַּעֲנִית כְּבָר עָבְרָה, אֵינוֹ צָרִיךְ לְהַשְׁלִים. הַגָּה: וְה"ה לְצִבּוּר שֶׁשָּׁמְעוּ אַחַר חֲצוֹת שֶׁקִּבְּלוּ הַתַּעֲנִית בְּטָעוּת, אֵינוֹ צָרִיךְ לְהַשְׁלִים (תה"ד סי' ר"פ).
An individual who is fasting over a trouble, and it became known that the trouble had already passed before he accepted the fast, need not complete it. Hagah [Rema]: And the same applies to a congregation that heard after midday that they had accepted the fast in error: they need not complete it (Terumat haDeshen, siman 280).
Shulchan Aruch, Orach Chayim — Torat Emet 363 edition, via Sefaria — public domain
English rendered from the Hebrew for this app — The Gematria's own rendering program. A rendering of the words, not a ruling; practical halacha is learned with a rav