Nehemiah 13:1-3

On that day the Book of Moses was read aloud as the people listened; and there was found written in it that no Ammonite or Moabite was ever to enter the assembly of God,

because they did not meet the sons of Israel with bread and water, but hired Balaam against them to curse them. However, our God turned the curse into a blessing.

So when they heard the Law, they excluded all foreigners from Israel. Tobiah Expelled and the Temple Cleansed