אורח חיים קמ״גOrach Chayim 143

Se’if 4ד׳

אִם נִמְצָא טָעוּת בְּסֵפֶר תּוֹרָה בִּשְׁעַת קְרִיאָה, מוֹצִיאִין סֵפֶר תּוֹרָה אַחֶרֶת, וּמַתְחִילִין מִמָּקוֹם שֶׁנִּמְצָא הַטָּעוּת, וּמַשְׁלִימִין הַקּוֹרִים עַל אוֹתָם שֶׁקָּרְאוּ בַּמֻטְעֶה; וְאִם נִמְצָא טָעוּת בְּאֶמְצַע קְרִיאַת הַקּוֹרֵא, גּוֹמֵר קְרִיאָתוֹ בַּסֵפֶר הַכָּשֵׁר, וּמְבָרֵךְ לְאַחֲרֶיהָ, וְאֵינוֹ חוֹזֵר לְבָרֵךְ לְפָנֶיהָ. הַגָּה: וְאִם כְּבַר קָרְאוּ עִמּוֹ ג' פְּסוּקִים וְאֶפְשָׁר לְהַפְסִיק, פּוֹסְקִים שָׁם, וּמְבָרֵךְ אַחֲרֶיהָ וּמַשְׁלִימִים הַמִּנְיָן בַּסֵּפֶר תּוֹרָה הָאַחֵר שֶׁמּוֹצִיאִין (מָרְדְּכַי פ"ב דִּמְגִלָּה) וְהָא דְּמוֹצִיאִין אַחֵר, דַּוְקָא שֶׁנִּמְצָא טָעוּת גָּמוּר, אֲבָל מִשּׁוּם חֲסֵרוֹת וִיתֵרוֹת אֵין לְהוֹצִיא אַחֵר, שֶׁאֵין סִפְרֵי תּוֹרָה שֶׁלָּנוּ מְדֻיָּקִים כָּל כָּךְ שֶׁנֹּאמַר שֶׁהָאַחֵר יִהְיֶה יוֹתֵר כָּשֵׁר (אָגוּר וּפִסְקֵי מהרי"א סי' ע' וְריא"ז וּמַהֲרִי"ל פָּסָק דְּאֵין לְהָבִיא סֵפֶר תּוֹרָה אַחֵר, וּבֵית יוֹסֵף פָּסַק דְּצָרִיךְ לְהוֹצִיא סֵפֶר תּוֹרָה אַחֵר לָכֵן צָרִיךְ לְחַלֵּק כָּךְ); וּבִשְׁעַת הַדַּחַק, שֶׁאֵין לַצִּבּוּר רַק סֵפֶר תּוֹרָה פָּסוּל וְאֵין שָׁם מִי שֶׁיָּכוֹל לְתַקְּנוֹ, יֵשׁ אוֹמְרִים דְּיֵשׁ לִקְרוֹת בּוֹ בְּצִבּוּר וּלְבָרֵךְ עָלָיו (כָּל בּוֹ וְאַבּוּדַרְהַם), וְיֵשׁ מַחֲמִירִין (תְּשׁוּבַת הָרַשְׁבָּ"א תפ"ז וְתת"ה וּמַיְמוֹנִי פ"י מֵהִלְכוֹת סֵפֶר תּוֹרָה); וְאִם חֻמָּשׁ אֶחָד שָׁלֵם בְּלֹא טָעוּת, יֵשׁ לְהָקֵל לִקְרוֹת בְּאוֹתוֹ חֻמָּשׁ, אַף עַל פִּי שֶׁיֵּשׁ טָעֻיּוֹת בָּאֲחֵרִים (רַ"ן).

If an error was found in a Torah scroll during the reading, they should take out another Torah scroll and begin [reading] from the place where the error was found, and complete the [number of] readers [i.e. aliyot] that are over [and above] those that were read [in the Torah] that had an error. And if the error was found in the middle reading, the reader should finish [that] reading in a valid Torah and blesses [the closing blessing] after it, and should not go back to bless [that's recited] before. Gloss: If they already read 3 verses along with [the verse that is in error] and it's possible to stop [where the error was found], they stop there and bless [the closing blessing] afterwards, and [then] they conclude the remaining count [of aliyot] in the other Torah scroll that they take out (Mordekhai - chapter 2 in Tractate Megillah). This - that we take out another [sefer Torah] - is specifically when a complete error is found, but if was only because of missing or extra letters, we don't take out another [sefer Torah], since our Torah scrolls are not so precise so as to say that the other one would be more valid (Agur and Piskei Mahari"a - siman 80 and Ria"z). And Mahari"l ruled that another Torah scroll should not be brought, and Beit Yosef ruled that another Torah scroll must be brought (and therefore, we need the above compromise). In an extenuating circumstance, where the congregation has only the invalid Torah scroll, and there is no one there who is able to fix it, there are those who say that it should be read from it and the blessings should be recited (Kol Bo and Abudarham), and some invalidate [it] (Teshuvat HaRashb"a 487 and 405?, and Maimoni on chapter 10 of Laws of a Torah Scroll). And if one of the chumashim [books of the Torah] is complete, without errors, one may be lenient and read from that specific chumash, even though there are errors in the others (Ra"n)

Se’if 5ה׳

בָּתֵּי כְּנֶסֶת שֶׁאֵין בָּהֶם מִי שֶׁיּוֹדֵעַ לִקְרוֹת אֶלָּא אֶחָד, יְבָרֵךְ וְיִקְרָא קְצָת פְּסוּקִים וִיבָרֵךְ לְאַחֲרֵיהֶם, וְיַחֲזֹר לְבָרֵךְ תְּחִלָּה וְקוֹרֵא קְצָת פְּסוּקִים וּמְבָרֵךְ לְאַחֲרֵיהֶם, וְכֵן יַעֲשֶׂה כַּמָּה פְּעָמִים, כְּמִסְפַּר הָעוֹלִים שֶׁל אוֹתוֹ הַיּוֹם.

[In] a synagogue that has only one person who knows how to read [Torah], that person should bless [the opening blessing] and read a few verses and then bless [the closing blessing] after them, then repeat [the process] and bless at the beginning, read a few verses, and bless afterwards. And [the reader] should continue doing so as many times as the number of people called up [for aliyot] for that day.