אורח חיים קצ״בOrach Chayim 192

Se’if 1א׳

הָיוּ הַמְּסֻבִּין ג', חַיָּבִים בְּזִמּוּן שֶׁאוֹמֵר אֶחָד מֵהֶם: נְבָרֵךְ שֶׁאָכַלְנוּ מִשֶּׁלּוֹ, וְהֵם עוֹנִים וְאוֹמְרִים: בָּרוּךְ שֶׁאָכַלְנוּ מִשֶּׁלּוֹ וּבְטוּבוֹ חָיִינוּ, וְהוּא חוֹזֵר וְאוֹמֵר: בָּרוּךְ שֶׁאָכַלְנוּ מִשֶּׁלּוֹ וּבְטוּבוֹ חָיִינוּ בָּרוּךְ אַתָּה ה' אֱלֹהֵינוּ מֶלֶךְ הָעוֹלָם הַזָּן אֶת הָעוֹלָם וְכו'; וְאִם הֵם ד' יָכוֹל לוֹמַר: בָּרְכוּ שֶׁאָכַלְנוּ מִשֶּׁלּוֹ, אֲבָל יוֹתֵר טוֹב לוֹמַר נְבָרֵךְ, שֶׁלֹּא לְהוֹצִיא עַצְמוֹ מִן הַכְּלָל; וְאִם הֵם עֲשָׂרָה, צָרִיךְ לְהַזְכִּיר אֶת ה', שֶׁאוֹמֵר: נְבָרֵךְ אֱלֹהֵינוּ וְכו', וְהֵם עוֹנִים וְאוֹמְרִים: בָּרוּךְ אֱלֹהֵינוּ וְכו'. וְאֵין לוֹמַר נְבָרֵךְ לֵאלֹהֵינוּ בְּלָמֶ "ד. וּבֵין שֶׁיִּהְיוּ עֲשָׂרָה אוֹ מֵאָה אוֹ אֶלֶף אוֹ רִבּוֹא, כָּךְ הֵם מְבָרְכִים; וְכָל הַמְשַׁנֶּה מִזֶּה הַנֻּסָח, כְּגוֹן שֶׁאוֹמֵר: נְבָרֵךְ עַל הַמָּזוֹן שֶׁאָכַלְנוּ, אוֹ שֶׁאוֹמֵר: לְמִי שֶׁאָכַלְנוּ מִשֶּׁלּוֹ, אוֹ שֶׁאוֹמֵר בִּמְקוֹם וּבְטוּבוֹ מִטּוּבוֹ, אוֹ בִּמְקוֹם חָיִינוּ אוֹמֵר חַיִּים, הֲרֵי זֶה בּוּר; וּכְשֶׁהֵם עֲשָׂרָה, כֵּיוָן שֶׁמַּזְכִּירִים אֶת הַשֵּׁם יָכוֹל לוֹמַר: נְבָרֵךְ אֱלֹהֵינוּ עַל הַמָּזוֹן שֶׁאָכַלְנוּ מִשֶּׁלּוֹ.

If those reclining were three, they are obligated in the zimmun (the summons for three who have eaten to bless together): one of them says, "Let us bless Him of whose bounty we have eaten", and they answer and say, "Blessed is He of whose bounty we have eaten and by His goodness we live"; and he repeats and says, "Blessed is He of whose bounty we have eaten and by His goodness we live. Blessed are You, Lord our God, King of the universe, who feeds the world, etc." And if they are four, he may say, "Bless Him of whose bounty we have eaten", but it is better to say "Let us bless", so as not to take himself out of the community. And if they are ten, he must mention the Name, saying, "Let us bless our God, etc.", and they answer and say, "Blessed is our God, etc." And one should not say "Let us bless to our God" with a lamed. And whether they are ten, or a hundred, or a thousand, or a myriad, so they bless. And anyone who departs from this wording — for example, who says "Let us bless for the food that we have eaten", or who says "to Him of whose bounty we have eaten", or who says "from His goodness" in place of "and by His goodness", or who says "the living live" in place of "we live" — this one is a boor. And when they are ten, since they mention the Name, he may say, "Let us bless our God for the food that we have eaten of His bounty."

Se’if 2ב׳

אִם טָעָה הַמְזַמֵּן בַּעֲשָׂרָה וְהָעוֹנִים, וְלֹא הִזְכִּירוּ אֱלֹהֵינוּ, אֵין יְכוֹלִים לַחֲזֹר; אֲבָל אִם עֲדַיִן לֹא עָנוּ אַחֲרָיו, יַחֲזֹר וִיזַמֵּן בַּשֵּׁם.

If the one who leads the zimmun among ten, and those who answer, erred and did not mention "our God", they cannot go back; but if they have not yet answered after him, he should go back and lead the zimmun with the Name.