Parashat Hayyei Sarah: Halakhah

Halakhah הֲלָכָה

When Avraham’s servant returns with Rivkah to her home, he is invited in for a meal. But before he has a bite to eat, he insists on first sharing his story to explain to Lavan who he is and what happened at the well.
The Torah doesn’t say why, but perhaps Avraham’s servant wanted to avoid eating and speaking at the same time! This is actually a rule in halakhah (referred to in Sforno’s commentary on Bereishit 24:19).
The Talmud warns against speaking while eating. Not only is it impolite; it can also be dangerous!
רַב נַחְמָן וְרַבִּי יִצְחָק הֲווּ יָתְבֵי בִּסְעוּדְתָּא אֲמַר לֵיהּ רַב נַחְמָן לְרַבִּי יִצְחָק לֵימָא מָר מִילְּתָא אֲמַר לֵיהּ הָכִי אָמַר רַבִּי יוֹחָנָן אֵין מְסִיחִין בִּסְעוּדָה שֶׁמָּא יַקְדִּים קָנֶה לְוֶשֶׁט וְיָבֹא לִידֵי סַכָּנָה
Rav Nahman and Rabbi Yitzhak were sitting at a meal. Rav Nahman said to Rabbi Yitzhak: “Let the Master share a word.” He said to him, “So said Rabbi Yohanan: One may not speak during a meal, perhaps the windpipe will precede the food pipe and cause danger (choking).”
There is a debate about whether this prohibition only applies when one is eating while reclining (which is how people used to eat at fancy meals, like on Seder night), when there is more danger in talking while eating.
Rabbi Eliezer Melamed cites positions on either side of this debate, and then writes as follows:
וּמִכָּל מָקוֹם, גַּם מִי שֶׁמֵּיקֵל, יַקְפִּיד עַל הַנִּימוּס, שֶׁדִּבּוּרוֹ יִהְיֶה בְּצוּרָה נָאָה, שֶׁלֹּא יִרְאוּ הַסּוֹעֲדִים אֶת הָאֹכֶל שֶׁבְּתוֹךְ פִּיו, וְקַל וָחֹמֶר שֶׁלֹּא יִנָּתְזוּ מִפִּיו שְׁיָרֵי מַאֲכָלִים תּוֹךְ כְּדֵי דִּבּוּרוֹ.
Nevertheless, even someone who is lenient [and thinks that the prohibition only applies while reclining] will make sure to speak in a polite manner, so that those eating will not see the food in your mouth, and certainly that no bits of food spit out of your mouth while speaking.

This is the Jewish source for the common rule: never speak with your mouth full!