The Inspiration for Birkat Hamazon

כִּ֚י יְהוָ֣ה אֱלֹהֶ֔יךָ מְבִֽיאֲךָ֖ אֶל־אֶ֣רֶץ טוֹבָ֑ה אֶ֚רֶץ נַ֣חֲלֵי מָ֔יִם עֲיָנֹת֙ וּתְהֹמֹ֔ת יֹצְאִ֥ים בַּבִּקְעָ֖ה וּבָהָֽר׃ אֶ֤רֶץ חִטָּה֙ וּשְׂעֹרָ֔ה וְגֶ֥פֶן וּתְאֵנָ֖ה וְרִמּ֑וֹן אֶֽרֶץ־זֵ֥ית שֶׁ֖מֶן וּדְבָֽשׁ׃ אֶ֗רֶץ אֲשֶׁ֨ר לֹ֤א

תֹּֽאכַל־בָּ֣הּ לֶ֔חֶם לֹֽא־תֶחְסַ֥ר כֹּ֖ל בָּ֑הּ אֶ֚רֶץ אֲשֶׁ֣ר אֲבָנֶ֣יהָ בַרְזֶ֔ל וּמֵהֲרָרֶ֖יהָ תַּחְצֹ֥ב נְחֹֽשֶׁת׃ וְאָכַלְתָּ֖ וְשָׂבָ֑עְתָּ וּבֵֽרַכְתָּ֙ אֶת־יְהוָ֣ה אֱלֹהֶ֔יךָ עַל־הָאָ֥רֶץ הַטֹּבָ֖ה אֲשֶׁ֥ר נָֽתַן־לָֽךְ׃

For the LORD your God is bringing you into a good land, a land with streams and springs and fountains issuing from plain and hill; a land of wheat and barley, of grape vines, figs, and pomegranates, a land of olive trees and [date] honey; a land where you may eat food without danger, where you will lack nothing; a land whose rocks are iron and from whose hills you can mine copper. When you have eaten your fill, give thanks to the LORD your God for the good land which God has given you.

אמר רב יהודה מנין לברכת המזון לאחריה מן התורה שנאמר (דברים ח, י) ואכלת ושבעת וברכת
Rav Yehuda said: From where is the mitzva by Torah law to recite Grace after Meals, derived? As it is stated: “And you shall eat and be satisfied and bless the Lord your God” (Deuteronomy 8:10).
ברכת המזון דכתיב (דברים ח, י) ואכלת ושבעת וברכת את ה' אלהיך בכל לשון שאתה מברך
§ It is stated in the mishna that Grace after Meals may be recited in any language. As it is written: “And you shall eat, and be satisfied, and bless the Lord your God” (Deuteronomy 8:10). The word “bless” is homiletically interpreted to mean: In any language that you bless.

(א) מִצְוַת עֲשֵׂה מִן הַתּוֹרָה לְבָרֵךְ אַחַר אֲכִילַת מָזוֹן שֶׁנֶּאֱמַר (דברים ח י) ״וְאָכַלְתָּ וְשָׂבָעְתָּ וּבֵרַכְתָּ אֶת יְיָ׳‎ אֱלֹהֶיךָ״. וְאֵינוֹ חַיָּב מִן הַתּוֹרָה אֶלָּא אִם כֵּן שָׂבַע שֶׁנֶּאֱמַר וְאָכַלְתָּ וְשָׂבָעְתָּ וּבֵרַכְתָּ. וּמִדִּבְרֵי סוֹפְרִים אָכַל אֲפִלּוּ כְּזַיִת מְבָרֵךְ אַחֲרָיו:

(1) It is an affirmative precept of the Torah to say Grace after a meal, as it is said, "And thou shalt eat and be satisfied and shalt bless the Lord, thy God" (Deuteronomy 8:10). The Torah only imposes the obligation on a person when he is satisfied; for it is said, "When thou hast eaten and art satisfied, thou shalt bless etc." According to the ordinances of the sages, however, even if one has eaten only as much food as the size of an olive, he recites Grace after the meal.