Q. Why does the Zimmun for the Grace After Meals (Bensching) require at least three males?
The reason why three constitutes a quorum (mezumman) has been variously explained. According to some, it recalls the custom of Abraham, with his invitation to his guests to join him in praising God.
The practice reflects two basic Jewish concepts – that one should share one’s food with others, especially the poor and needy, and that the praise of God is the greater when uttered by a company: “In the multitude of people is the Kind glorified” (Prov. 14:28).