The source of Birkas HaMazon is in a passuk in this week’s Parsha, “you will eat and be satisfied and bless Hashem etc.” The Avudarham comments that there is an extra word, “es,” before the name of Hashem in the passuk.
He says that this hints at the requirement of a person to give a blessing to his host after the meal.
Rabbi Aharon Dovid Singer
Rosh Kollel, NMB Kollel
305-972-6508