אמר רב יהודה מנין לברכת המזון לאחריה מן התורה שנאמר (דברים ח, י) ואכלת ושבעת וברכתOr, in English:
Rab Judah said: Where do we find that the grace after meals is ordained in the Torah? Because it says: And thou shalt eat and be satisfied and bless.3That pasuk, in Devarim 8, in Ekev, reads:
|י וְאָכַלְתָּ, וְשָׂבָעְתָּ--וּבֵרַכְתָּ אֶת-ה אֱלֹהֶיךָ, עַל-הָאָרֶץ הַטֹּבָה אֲשֶׁר נָתַן-לָךְ.||10 And thou shalt eat and be satisfied, and bless the LORD thy God for the good land which He hath given thee.|
One can certainly read this as a command, on a peshat level. But Shadal explains it as follows, and makes a rather good point:
וברכת: לפי הפשט אין זה ציווי, רק הודעה שכל כך תהיה טובתך והצלחתך, עד כי מעצמך תכיר חסד הבורא ותתעורר לברכו; ואח"כ הזהיר שישמרו לבלתי שכוח כי מה' היתה זאת להם. כי כן טבע האדם כשתבואהו טובה גדולה, הוא מברך את ה', אך אח"כ ברוב הימים הטובה נעשית לו טבעית, והוא שוכח מצבו הקודם."And bless: According to the peshat, this is not a command [to bless]; rather, it informing that so good will be your good and success, to such an extent that of your own you will recognize the Creator and be stirred up to bless him. And after that [in the following pesukim] it warns to be careful lest you forget that from Hashem was this to them. For such is the nature of man, when a great good comes to him, he blesses Hashem, but afterwards, with the great number of days of good, it becomes natural to him, and he forgets his former situation."
In other words, not tzivuy, but telling us just how good it will be. Meanwhile, even the Karaites take it as a tzivuy and obligation. Thus, Aaron the Karaite writes:
The alternative to Shadal, on the level of peshat, is that the vav of וּבֵרַכְתָּ is telling you the necessary conclusion. And indeed, we should contrast it with the alternative, appearing later in the perek:
The proper response to וְאָכַלְתָּ וְשָׂבָעְתָּ, the Torah is telling us, is וּבֵרַכְתָּ אֶת-ה אֱלֹהֶיךָ.
Perhaps this is in your heart, in parallel and contrast to וְאָמַרְתָּ בִּלְבָבֶךָ in pasuk 17. But say that a beracha is out loud.
Even so, peshat in this pasuk is not bentching. It is a recognition, every once in a while, when living the good life in the land of Israel, and then thanking Hashem, either in your heart or out line.
What we see in the gemara is a derasha, that every time you literally eat until you are satiated, you must make a blessing. Perhaps when one blesses
This does not mean that this derasha does not create a chiyuv deoraysa; or that while bentching with proper intent, you are not in this manner fulfilling the peshat interpretation of the pasuk.
Separate from this, on a peshat level, is this only thanking for the land?