Parshas Ki Seitzei bars an Ammonite or Moavite from marrying into the Jewish people even unto the tenth generation. While an Edomite and Egyptian may marry in the third generation. What's the fundamental basis for the distinction? The ban on Ammon and Moav follows that of the one on bastards and indeed both nations are the products of incest. Improper relations of this sort are occasionally referred to in the Torah as "Chessed" or kindness because they have the appearance of love to them. The distinction goes to the two types of anti-Semitism defined by the Edomites and the Moavites. Edom and Egypt were open in their hostility toward the Jews. They sought to persecute and kill them. Whatever malice they had depends on their strength and their national power. By the third generation they no longer present a danger. However Ammon and Moav represents a more insidious form of corruption as they demonstrated by hiring Bilaam and then attempting to corrupt the Jews. R...