Siman 179
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 גָּמַר סְעוּדָתוֹ וְנָטַל יָדָיו מַיִם אַחֲרוֹנִים, אֵינוֹ יָכוֹל לֶאֱכֹל וְלֹא לִשְׁתּוֹת, עַד שֶׁיְּבָרֵךְ בִּרְכַּת הַמָּזוֹן; וְאִם אָמַר: הַב לָן וּנְבָרֵךְ, הָוֵי הֶסַח הַדַּעַת וְאָסוּר לוֹ לִשְׁתּוֹת אֶלָּא אִם כֵּן יְבָרֵךְ עָלָיו תְּחִלָּה, וַאֲכִילָה דִּינָהּ כִּשְׁתִיָּה לְהָרֹא"שׁ; אֲבָל לְהר"ר יוֹנָה וְהָרַ"ן אֲכִילָה שָׁאנֵי, שֶׁאַף עַל פִּי שֶׁסִלֵּק יָדוֹ מִלֶּאֱכֹל וַאֲפִלּוּ סִלְּקוּ הַשֻּׁלְחָן אִם רָצָה לַחֲזֹר לַאֲכִילָתוֹ אֵינוֹ צָרִיךְ לְבָרֵךְ פַּעַם אַחֶרֶת, שֶׁכָּל שֶׁלֹּא נָטַל יָדָיו לֹא נִסְתַּלֵּק לְגַמְרֵי מֵאֲכִילָה.
1 Which things are considered a lapse of attention during a meal requiring a new blessing. 6 sections: If one finished his meal and washed his hands with the final waters, he may not eat or drink until he recites Grace After Meals. If he said "let us say the blessing" this constitutes a lapse of attention and he may not drink unless he first recites a blessing over it. Eating has the same law as drinking according to the Rosh; but according to Rabbeinu Yonah and the Ran, eating is different — even though he withdrew from eating, and even if the table was removed, if he wishes to return to eating he need not recite a blessing again, since as long as he has not washed his final waters he has not fully withdrawn from eating.
ב מִי שֶׁסוֹמֵךְ עַל שֻׁלְחַן אֲחֵרִים, אֲפִלּוּ אָמַר: הַב לָן וּנְבָרֵךְ, לָא הָוֵי הֶסַח הַדַּעַת עַד שֶׁיֹּאמַר בַּעַל הַבַּיִת.
2 One who depends on another's table — even if he said "let us say the blessing" it is not considered a lapse of attention until the host says so.
ג אִם לֹא אָמַר הַב לָן וּנְבָרֵךְ וְגַם לֹא נָטַל יָדָיו מִשֶּׁנָּטַל הַכּוֹס לְבָרֵךְ, הָוֵי הֶסַח הַדַּעַת.
3 If he did not say "let us say the blessing" and also did not wash his final waters — once he has taken the cup to recite the blessing it is considered a lapse of attention.
ד כְּשֶׁאָדָם נִכְנָס לְבֵית חֲבֵרוֹ וְיֵשׁ שָׁם חֲבוּרוֹת הַרְבֵּה שֶׁאוֹכְלִים וְכָל אֶחָד מוֹשִׁיט לוֹ כּוֹס, יֵשׁ מִי שֶׁאוֹמֵר שֶׁמְּבָרֵךְ עַל כָּל אֶחָד בּוֹרֵא פְּרִי הַגֶּפֶן, כִּי בְּכָל פַּעַם הוּא נִמְלָךְ.
4 When a person enters his friend's house and there are many groups eating, and each one offers him a cup — some say he recites borei pri hagafen over each one, since each time he is reconsidering.
ה הַקְּרוּאִים בְּבֵית בַּעַל הַבַּיִת לֶאֱכֹל מִינֵי פֵּרוֹת, וּמְבִיאִין לָהֶם בָּזֶה אַחַר זֶה, אֵינָם צְרִיכִים לְבָרֵךְ אֶלָּא עַל הָרִאשׁוֹן.
5 Guests invited to a host's home to eat various fruits, and they are brought to them one after another — they need only recite a blessing over the first.
ו אָכַל כָּל מַאֲכָל וְלֹא אָכַל מֶלַח, שָׁתָה כָּל מַשְׁקֶה וְלֹא שָׁתָה מַיִם, בַּיּוֹם יִדְאַג מִפְּנֵי רֵיחַ הַפֶּה, וּבַלַּיְלָה מִפְּנֵי רֵיחַ הַפֶּה וּמִפְּנֵי אַסְכָּרָה (פי' חֹלִי חוֹנֵק); וְהָאוֹכֵל מֶלַח אַחַר אֲכִילָתוֹ לֹא יֹאכַל בְּגוּדָל (גּוּדָל הוּא הַאֶצְבַּע הַגַּס, אֶצְבַּע הוּא קָרוֹב לַגַּס, אַמָּה הָאָרֹךְ, קְמִיצָה הוּא הַסָמוּךְ לַקָטָן, זֶרֶת הוּא הַקָטָן), דְּקָשֶׁה לִקְבֹּר בָּנִים; וְלֹא בַּזֶּרֶת, דְּקָשֶׁה לַעֲנִיּוּת; וְלֹא בָּאֶצְבַּע, דְּקָשֶׁה לש"ד, אֶלָּא בָּאַמָּה וּבַקְּמִיצָה וְעַיֵּן לְעֵיל סי' ק"ע לָמָּה אֵין אָנוּ נוֹהֲגִין בַּאֲכִילַת מֶלַח וּשְׁתִיַּת מַיִם.
6 If one ate any food and did not eat salt, or drank any beverage and did not drink water — by day he should be concerned about bad breath, and by night he should be concerned about both bad breath and croup (a choking illness). One who eats salt after his meal should not eat it with his thumb — as it is harmful for burying children — nor with the little finger — as it is harmful for poverty — nor with the index finger — as it is harmful for bloodshed — but rather with the middle finger or the ring finger. (See above §170 for why we no longer practice eating salt and drinking water.)