The Torah places great emphasis upon the imperative to distance the nations of Amon and Moav from our midst. Why? What did these nations do that was so invidious that they may never be accepted into the fold of Judaism? What crime did they commit that castigates them for all time? The Torah offers two responses. First, they did not come forward and welcome us with food when we passed by them during our trek in the desert. Second, they hired Bilaam to work against us. These actions, especially the second one, are unquestionably reprehensible. Are they worse, however, than the acts which the Egyptians committed against us? Are we to ignore two hundred and ten years of suffering, torment and murder?
Nebuchadnezzer and Titus were reshaim who destroyed the Bais Hamikdash. Yet their descendants are permitted to marry into the Jewish nation. The Ramban addresses this question. He offers a classical response that goes to the foundation of the Jewish People, demonstrating the caliber of refinement that is demanded of the Jewish personality. He writes that Amon and Moav were descendants of individuals who benefited from Avraham Avinu’s kindnesses. Avraham had saved Lot and his family from the destruction that befell Sodom. Lot had fathered Amon and Moav. The key that elucidates the enigma of Amon and Moav is hakoras tov, appreciation/gratitude. Amazing! Because their ancestor was saved by our ancestor, Avraham, they were obliged to us; they should have been makir tov. The root of their iniquity is their lack of appreciation, their refusal to acknowledge the benefit that they received.
By nature, man thinks first and foremost of himself. He leaves little room for others. The middah of chesed, kindness, is a characteristic transmitted to us by Avraham Avinu, the pillar of chesed. Everyone possesses an element of this character trait, although some people manage to bury it deep in their personalities. If one does not go out of his way to be kind to others, however, we cannot sever him from the human race, since we expect man to be egotistical by nature. Hakoras tov is a character trait which is inherent in every human being. Who does not repay those who are kind to him? What kind of human being would ignore those who benefited him? Such a person is repulsive, his actions contemptible. He has isolated himself from humanity by his refusal to recognize and repay those who have helped him. Amon and Moav acted in a despicable manner. They demonstrated their unworthiness to be viewed as human beings at all, let alone to be accepted into the Jewish nation.