The Ammonites: Jewish Laws Respecting: Perpetual Exclusion from the Congregation
Source: TTT
Deuteronomy 23:3
No Ammonite or Moabite or any of their descendants may enter the assembly of the LORD, even to the tenth generation.
Nehemiah 13:1
At that time the Book of Moses was read aloud in the hearing of the people, and in it they found the passage stating that no Ammonite or Moabite should ever enter the assembly of God,