The beginning of Parshat Eikev contains a series of Pesukim that lead to two questions. “VeAchalta VeSavata UVeirachta Et Hashem Elokecha,” “You will eat and you will be satisfied, and bless Hashem your God” (Devarim 8:10). While from a purely Biblical perspective, it seems that one must only recite Birchat HaMazon when one is satisfied with one’s meal, Chazal mandated that a Jew bless Hashem even if he is not satisfied, as long as he has eaten a KeZayit, an olive’s worth, of bread. Why did Chazal feel the need to institute this law if the Torah explicitly states that one should bless only after having been satisfied? Additionally, the Torah continues to describe that Hashem gave Bnei Yisrael the Man “Lemaan Nasotecha,” “In order to test you” (Devarim 8:16). How can the daily provision of divine ready-made food from the sky be called a test?
There were many among Bnei Yisrael who did not appreciate the Man as the perfect food for them; these people wanted what they thought was better food. On the other hand, there were many of Bnei Yisrael who valued the Man so much that they did not want to go into Eretz Yisrael because they were afraid to lose such easy access to food. Both of these groups of people were punished; the former because they did not appreciate what Hashem did for them and the latter because they cherished the gift of the Man more than the gift of Eretz Yisrael. The test of the Man is now clear: one had to find the perfect balance of appreciation for the Man; one could not become too attached to the Man while at the same time one was obligated to recognize the Mann as the best possible food for that time.
Chazal understood from this that when Bnei Yisrael are in Galut, Hashem provides for us, as he does today, and for this we must properly show gratitude. But they did not want us to become too satisfied with what Hashem provides, as we can never be truly satisfied without the Beit HaMikdash. Chazal therefore mandated that we recite Birchat HaMazon even when we are not yet satisfied in order to remind us that we will never be truly satisfied until we are out of the Galut and we once again have Hashem’s presence among us with the coming reign of Mashiach.