Siman 66
Presented here for study, not as a practical ruling. The Shulchan Aruch rules by Sephardi custom, the Rema's glosses by Ashkenazi custom, and the Kitzur follows Ashkenazi custom. For a practical question, ask your rabbi.
א בֵּין הַפְּרָקִים שׁוֹאֵל בִּשְׁלוֹם אָדָם נִכְבָּד וּמֵשִׁיב שָׁלוֹם לְכָל אָדָם, וּבָאֶמְצַע שׁוֹאֵל בִּשְׁלוֹם מִי שֶׁהוּא יָרֵא מִמֶּנּוּ, כְּגוֹן אָבִיו אוֹ רַבּוֹ, אוֹ מִי שֶׁהוּא גָּדוֹל מִמֶּנּוּ בְּחָכְמָה, וְכָל שֶׁכֵּן מֶלֶךְ אוֹ אַנָּס. וּמֵשִׁיב שָׁלוֹם לְאָדָם נִכְבָּד, וַאֲפִלּוּ בְּאֶמְצַע הַפָּסוּק, חוּץ מִפָּסוּק שְׁמַע יִשְׂרָאֵל וּבָרוּךְ שֵׁם כְּבוֹד מַלְכוּתוֹ לְעוֹלָם וָעֶד, שֶׁלֹּא יַפְסִיק בָּהֶם כְּלָל, אִם לֹא מִפְּנֵי מִי שֶׁיָּרֵא שֶׁמָּא יַהַרְגֶנּוּ:
1 [The Laws Regarding] In Which Place One May Interrupt and in Which Place One May Not Interrupt. Containing 10 Se-ifim Between the sections [of Shema or it's blessings], one may greet an honored person and respond to a greeting from any person. And in the middle [of a section], one may greet someone that one reveres, such as one's father, one's teacher, or one greater than oneself in wisdom, and all the more so a king or one who compels. And one may respond to a greeting from an honored person, even in the middle of a verse, except for the verse of "Sh'ma Yisrael" and "Baruch shem kavod malchuto l'olam va-ed", during which one may not interrupt at all unless it is out of fear that he will be killed.
ב אִם שָׁכַח לְהָנִיחַ צִיצִית וּתְפִלִּין יָכוֹל לְהַפְסִיק בֵּין הַפְּרָקִים לַהֲנִיחָם, וִיבָרֵךְ עֲלֵיהֶם: הַגָּה: וְיֵשׁ אוֹמְרִים שֶׁלֹּא יְבָרֵךְ עֲלֵיהֶם עַד אַחַר הַתְּפִלָּה, וְהָכֵי נָהוּג לְעִנְיַן טַלִּית (בֵּית יוֹסֵף).
2 If one forgot to don tzitzit or tefillin, one can interrupt between sections [of Shema or it's blessings] and don them, and one can make a blessing over them. Rema: And there are those who say one should not make a blessing over them until after the Prayer [Amidah], and such is the custom with regard to tallit (Beit Yosef)
ג לְקַדִּישׁ וְלִקְדֻשָּׁה וּלְבָרְכוּ מַפְסִיק אֲפִלּוּ בְּאֶמְצַע הַפָּסוּק, וְכֵן לְמוֹדִים, אֲבָל לֹא יֹאמַר אֶלָּא תֵּבַת מוֹדִים בִּלְבַד: הַגָּה: וְכֵן בְּבָרְכוּ לֹא יֹאמַר יִתְבָּרַךְ וְיִשְׁתַּבַּח וְכו', וְיֵשׁ אוֹמְרִים דְּאָמֵן שֶׁעוֹנִין אַחַר בִּרְכַּת הָאֵל הַקָּדוֹשׁ וְאַחַר שׁוֹמֵעַ תְּפִלָּה יֵשׁ לוֹ דִּין קְדֻשָּׁה, וְיוּכַל לַעֲנוֹת אוֹתָם בִּקְרִיאַת שְׁמַע וְכֵן עִקָּר וּלְכָל ה"מ פּוֹסְקִים מִכָּל שֶׁכֵּן בְּאוֹמֵר תַּחֲנוּנִים (תְּשׁוּבַת הָרַשְׁבָּ"א).
3 For Kaddish, K'dushah, and Bar'chu, one interrupts [Shema or it's blessings] even in the middle of a verse. And so too for Modim, but one [should] only say the word "Modim" alone. Rema: And also, regarding [answering] Barchu [between or in the middle of sections] (which is allowed), one should not say "yitbarach v'yishtabach, etc." (ie. there is an old custom in some places where the congregation would say "yitbarach v'yishtabach, etc." while the leader is saying Barchu). And there are those who say that the "Amen" that we respond with after the blessing of "ha-El ha-Kadosh" ("the Holy God" - at the end of the K'dushah in Shemona Esrei) and after "shomeya tefilah" ("the one who hears prayer" in Shemona Esrei) has the status of the K'dushah, and one can answer them during the Recitation of the Sh'ma. And that is the main opinion [that should be followed]. And with all these things, we interrupt, and certainly when saying supplications [Teshuvot of the Rashba]
ד כֹּהֵן שֶׁהָיָה קוֹרֵא קְרִיאַת שְׁמַע וּקְרָאוּהוּ לִקְרוֹת בַּתּוֹרָה, יֵשׁ מִי שֶׁאוֹמֵר שֶׁמַּפְסִיק וְיֵשׁ מִי שֶׁאוֹמֵר שֶׁאֵינוֹ מַפְסִיק, וַהֲלָכָה כִּדְבָרָיו.
4 If a Kohen [priest] was reciting the Recitation of the Sh'ma and they called him to the Torah: there is [an opinion] that says that one interrupts [the recitation for the aliyah] and there is [an opinion] that says one does not interrupt. And the halachah is according to his words (ie. the latter).
ה וְאֵלּוּ הֵן בֵּין הַפְּרָקִים, בֵּין בְּרָכָה רִאשׁוֹנָה לִשְׁנִיָּה, בֵּין שְׁנִיָּה לִשְׁמַע, בֵּין שְׁמַע לִוְהָיָה אִם שָׁמוֹעַ, בֵּין וְהָיָה אִם שָׁמוֹעַ לְוַיֹּאמֶר, אֲבָל בֵּין וַיֹּאמֶר לֶאֱמֶת וְיַצִּיב לֹא יַפְסִיק, שֶׁלֹּא לְהַפְסִיק בֵּין ה' לֶאֱמֶת, אֶלָּא יֹאמַר אֲנִי ה' אֱלֹהֵיכֶם אֱמֶת, וְאָז יַפְסִיק כְּדִין בְּאֶמְצַע הַפֶּרֶק.
5 These are [what are considered] "between the sections": between the first blessing and the second, between the second and Sh'ma, between Sh'ma and V'Haya Im Sh'moa [the second paragraph of the Recitation of the Sh'ma], between V'Haya Im Sh'moa and Va-yomer [the third paragraph]. But between Va-yomer and "Emet V'yatziv", we do not interrupt, because we do not interrupt between the LORD and Emet, rather one should say "ani the LORD Eloheichem emet" and then interrupt as in the case of the middle of a section.
ו אִם פָּסַק מִפְּנֵי הַיִּרְאָה אוֹ הַכָּבוֹד אַחַר שֶׁאָמַר אֱמֶת, אוֹ שֶׁסִיֵּם קֹדֶם הַחַזָּן, וְסָמַךְ ה' אֱלֹהֵיכֶם עִם אֱמֶת, וּמַמְתִּין שֶׁיַּתְחִיל הַחַזָּן וְשֶׁיֹּאמַר עִמּוֹ, אֵינוֹ צָרִיךְ לַחֲזֹר וְלוֹמַר פַּעַם אַחֶרֶת אֱמֶת.
6 If one stopped because of the feared or honored [person] after they [concluded Shema and] said "emet" or they finished [Shema] before the chazzan, [meaning:] they joined "The LORD Eloheichem" with "emet", and are now waiting for the chazzan to begin [so that they can say it] with him, there is no need to go back and say "emet" another time [because one interrupted the sentence].
ז אֵינוֹ אוֹמֵר אָמֵן אַחַר גָּאַל יִשְׂרָאֵל, מִשּׁוּם דְּהָוֵי הֶפְסֵק: הַגָּה: וְיֵשׁ אוֹמְרִים דְּעוֹנִין אָמֵן, וְכֵן נוֹהֲגִין לַעֲנוֹת אַחַר הַשְּׁלִיחַ צִבּוּר אָמֵן, אֲבָל אִם הִתְפַּלֵּל לְבַד אֵין עוֹנִין אָמֵן כְּדִלְקַמָּן סִימָן רט"ו (טוּר).
7 One should not answer amen after [the blessing of] "ga'al Yisrael", because this is considered an interruption [between the Recitation of the Sh'ma and the Amidah]. Rema: There are those who say that we do respond "amen", and that is our custom, to answer "amen" after the prayer leader. But if one prayed alone, he should not respond amen [to his own blessing], as below in Siman 215 [Tur].
ח צָרִיךְ לִסְמֹךְ גְּאֻלָּה לִתְפִלָּה, וְלֹא יַפְסִיק לְאַחַר שֶׁאָמַר גָּאַל יִשְׂרָאֵל, רַק אִם אֵרְעוֹ אֹנֶס שֶׁלֹּא הֵנִיחַ תְּפִלִּין, וְנִזְדַּמְּנוּ לוֹ בֵּין גְּאֻלָּה לִתְפִלָּה, מֵנִיחַ אָז, וְלֹא יְבָרֵךְ עֲלֵיהֶם עַד אַחַר שֶׁיִּתְפַּלֵּל. אֲבָל טַלִּית לֹא יָנִיחַ אָז, וְאִם עַד שֶׁלֹּא אָמַר גָּאַל יִשְׂרָאֵל נִזְדַּמְּנוּ לוֹ טַלִּית וּתְפִלִּין, מְנִיחָן, וְלֹא יְבָרֵךְ עֲלֵיהֶם עַד אַחַר תְּפִלָּה: הַגָּה: וְיֵשׁ אוֹמְרִים שֶׁקֹּדֶם גָּאַל יִשְׂרָאֵל יְבָרֵךְ עַל הַתְּפִלִּין וְהָכֵי נָהוּג (מָרְדְּכַי וְתוס' וְהַגָּהוֹת מַיְמוֹנִי מה' קְרִיאַת שְׁמַע).
8 One needs to adjoin [the Blessing of] Redemption to the Amidah, and one may not interrupt after they said "ga'al Yisrael", unless there was an unavoidable circumstance - for example, they did not wear tefillin (ie. they did not have a pair of tefillin up until then) and then [the tefillin] became available between Redemption and the Amidah, [in such a case, they should] don them right then but they should not bless over them until after they pray [the Amidah]. But [regarding] a tallit, one should not put it on at that point. But if one did not yet say "ga-al Yisrael", and now a tallit and tefillin become available, they don them [right then] but should not bless over them until after the Amidah. Rema: And there are those who say that prior to "ga-al Yisrael" one should bless over the tefillin, and such is our custom [Mordechi and Tosefot and Hagahot Maimoni from Hilchot Kriat Sh'ma]
ט אֵין לַעֲנוֹת קַדִּישׁ וּקְדֻשָּׁה בֵּין גְּאֻלָּה לִתְפִלָּה, וְכֵיצַד עוֹשֶׂה, מַמְתִּין בְּשִׁירָה חֲדָשָׁה כְּדֵי לַעֲנוֹת.
9 One should not respond to Kaddish or Kedushah between Redemption and the Amidah. What should he do? He should wait at [the words] "shira chadasha" in order to respond.
י כָּל מִי שֶׁלֹּא אָמַר אֱמֶת וְיַצִּיב שַׁחֲרִית, וֶאֱמֶת וֶאֱמוּנָה עַרְבִית, לֹא יָצָא יְדֵי חוֹבַת הַמִּצְוָה כְּתִקְנָהּ: הַגָּה: מִי שֶׁהוּא אָנוּס וְדָחוּק, וְאֵין לוֹ פְּנַאי לְהִתְפַּלֵּל, מִיָּד אַחַר קְרִיאַת שְׁמַע יִקְרָא קְרִיאַת שְׁמַע עַד אֱמֶת, וְיַמְתִּין לוֹמַר שְׁאָר הַבְּרָכָה עַד שֶׁיִּתְפַּלֵּל, שֶׁאָז יֹאמַר וְיַצִּיב וְנָכוֹן כו', וְיִתְפַּלֵּל כְּדֵי שֶׁיִּסְמֹךְ גְּאֻלָּה לִתְפִלָּה (בֵּית יוֹסֵף בְּשֵׁם רוֹקֵחַ סִימָן שכ"א):
10 Anyone who did not say "Emet V'yatziv" in the morning service and "Emet V'Emunah" in the evening service has not fulfilled their obligation of the commandment as as it should have been. Rema: One who had an unavoidable circumstance and is pressed [for time] and does not have time to pray [Shemona Esrei] immediately after the Recitation of the Sh'ma: they should recite the Sh'ma until [the word] "emet" and then wait to say the rest of the blessing until they can pray [Shemona Esrei]. And then they say "v'yatziv v'nachon" etc. and then pray [Shemona Esrei] in order adjoin Redemption to the [Shemona Esrei] prayer [Beit Yosef in the name of Rokeach, chapter 321].