An Ammonite or Moavite may not enter the nation of Hashem, even until the tenth generation, to eternity...because he hired Bilaam son of Beor... to curse you. (23:4,5). In reality, these two nations could complain to Hashem, why are we not allowed to marry into Klal Yisrael, it is not our fault you created us to be stingy. The answer is as follows with a Maashel, parable.
There once lived a Jewish man that left this world and came before the high court in Heaven. He was asked, “Did you give charity?” He answered “No. Hashem created me with a stingy nature.” The high court answered, “If this is true you are dismissed and go into Gan Eden.” Upon arrival to Gan Eden, the angel asked him, “I understand you did not give charity because of your nature, let me ask you, did you lavish jewelry for your wife? Did you not wear the most expensive clothing? If Hashem created you to be stingy how did you buy all these expensive things?” You are not stingy by nature. The angel sent him away.
The same is when the nations claim that they were created to be stingy, Hashem will ask, why did you hire Bilaam for a fortune of money to curse the Jewish nation? If you were stingy by nature, you would have never paid the exorbitant amounts. That is why they were punished for not entering the nation of Hashem.
