The Torah in Parashat Eikev (8:10) introduces the mitzva of birkat ha-mazon, which requires reciting a blessing after eating: “You shall eat and be satiated, and you shall bless the Lord your God for the good land which He has given you.”
One of the intriguing halakhot relevant to birkat ha-mazon is the obligation of zimun. If three or more halakhic adults ate together, they are required to formally introduce birkat ha-mazon by one of them announcing an “invitation” to the others to bless the Almighty who has provided them with food. The other express their “consent,” and they then begin birkat ha-mazon. In the past, when birkat ha-mazon was recited in the framework of a zimun, one person would recite the blessing for the entire group, all of whom would listen silently and answer “amen” at the conclusion of each berakha.
An insightful explanation of the meaning and significance of zimun is suggested by Rav Shimshon Raphael Hirsch, in his Torah commentary (here in Parashat Eikev):
If nothing tends more to throw men back on to their own selves, and is liable to make each man a competitor to his neighbor than the struggle for food, then this fellowship in eating and in saying the Beracha should, so it seems to us, bring about freeing such feelings of selfish thoughts by calling to mind thoughts of the Goodness of God being directed to all at the same time simultaneously in the same way.
The recitation of birkat ha-mazon, as clearly emerges from the context in which it is presented here in Parashat Eikev, is intended to direct our attention to the fact that God provides us our needs and sustains us. Even though it appears that we obtain food and our other necessities through our hard work and ingenuity, we are bidden to “remember that it is He who gives you the strength to achieve wealth” (8:18). Moshe tells Benei Yisrael that once they leave the miraculous existence of the wilderness and begin tilling the land and partaking of the food they produce through their own efforts, they must attribute their successes to God, and remember that ultimately, only He provides their sustenance, and this message underlies the birkat ha-mazon obligation.
For this very reason, Rav Hirsch explains, Chazal established the zimun, whereby people join together to collectively express their gratitude to God as a single group and organic unity. The pursuit of a livelihood, by its very nature, entails fierce competition, as each individual must struggle for his or her piece of the collective pie, whether it’s in the form of a job, a promotion, a grant, or some other avenue of sustenance. By joining together to recite birkat ha-mazon as a group, we reinforce our awareness that God is the one who provides our needs, and He is fully capable of simultaneously and adequately caring for all of us. The institution of zimun reflects the notion that birkat ha-mazon, acknowledging God as the ultimate source of our livelihood, has the effect of bringing us together and helping us overcome the tension and friction that the difficult quest for sustenance so often creates. Once we recognize that it is God who provides our needs, and that His capabilities are unlimited, we naturally reduce the degree of competitiveness and fight which we bring with us to the workplace, as we fully trust that God is perfectly capable of feeding us all. This recognition reminds us that we should all be working together, not against one another, in our efforts to secure a livelihood, and in expressing our profound gratitude to the Almighty each day for all He gives us.