The Biblical injunction to say grace after meals is ordained only when one has eaten to satiation, as the verse says: “You shall eat, be satisfied, and bless Hashem for the good land”. If one eats but does not feel full there is no Biblical directive to bentch, but there is a Rabbinical requirement to say grace, providing he has consumed bread the volume of an olive.
Why should thanking Hashem be dependent on satiation? Shouldn’t we be grateful for every morsel? G-d has provided the nourishment to keep body and soul together, and yet since one is not full, there is no imperative to thank Him?
Of course one has to thank Hashem for everything; however a person needs the correct frame of mind to fully express his thanks. A person whose stomach is growling and feels underfed, may not have the correct presence of mind when expressing his gratitude. Rather than a person accustom himself to half baked thanks, the Torah wanted that a person to be in the optimum mode for saying grace.
The Rabbis however, wanted a person to exert himself above his inclination and bless Hashem even if conditions are not most favorable.
The purpose of grace is not to thank. The blessing after the meal has an entirely different function. The Torah writes elsewhere “Yeshuren waxed and revolted” – over indulgence misleads man into taking his successes for granted, attributing one’s rise to power to one’s own strengths and efforts. Conversely the poor man has an easier time connecting his accomplishments to Hashem’s intervention. That is why the Torah only requires a person who eats to satiation to bless Hashem for his food. At the point of satiation he enters the danger zone, and needs to reinforce recognition the true Source of his food.
This is supported by the juxtaposing verse, “Guard yourself lest you forget Hashem” indicating the grace after meals is a measure to prevent us, G-d forbid, from forgetting Hashem.
What do you think about when you Bentch?
Rabbi Yisroel Lipkin who is more famously known as Rabbi Yisroel Salanter was the father of the Mussar Movement. On one of his many travels he visited Frankfurt um Main and his host was none other than the renowned Baron Rothschild.
The Rothschilds, an extremely wealthy had made their money in the banking industry. Their sucess was fueled by a family network throughout the major European cities, with each brother residing in a different city. Baron Rothschild was in charge of the main branch of Frankfurt. On personal level the Baron was a man who was deeply religious, a man devoted to Halachah and Yiddishkeit.
When Reb Yisroel came to visit, the Baron gave him a grand tour of his mansion, constantly pointing out to the Gadol Hador how everything in his home conformed to Halachah. Once the expedition had finished, Reb Yisroel who was noted for his brilliant mind, said to the Baron “there is one aspect of your home that doesn’t fit with the Torah”.
The Baron was taken aback “What it the matter? What have I done wrong?”
Reb Yisroel replied with a glint in his eye, “The Torah says that ‘Yeshurun waxed and revolted against his religion’ I see that despite the fact you have grown wealthy, you still adhere strongly to Halachah”.
If one forgot Rezei at the third meal of Shabbos one does not have to repeat Birkas Hamozon.