Deuteronomy 23:3-6
“An Ammonite or Moabite shall not enter the assembly of the Lord; even to the tenth generation none of his descendants shall enter the assembly of the Lord forever, because they did not meet you with bread and water on the road when you came out of Egypt, and because they hired against you Balaam the son of Beor from Pethor of Mesopotamia, to curse you. Nevertheless the Lord your God would not listen to Balaam, but the Lord your God turned the curse into a blessing for you, because the Lord your God loves you. You shall not seek their peace nor their prosperity all your days forever.
On that day they read from the Book of Moses in the hearing of the people, and in it was found written that no Ammonite or Moabite should ever come into the assembly of God, because they had not met the children of Israel with bread and water, but hired Balaam against them to curse them. However, our God turned the curse into a blessing. So it was, when they had heard the Law, that they separated all the mixed multitude from Israel. Now before this, Eliashib the priest, having authority over the storerooms of the house of our God, was allied with Tobiah.
But Ruth said:
“Entreat me not to leave you,
Or to turn back from following after you;
For wherever you go, I will go;
And wherever you lodge, I will lodge;
Your people shall be my people,
And your God, my God.
So Ruth the Moabitess said to Naomi, “Please let me go to the field, and glean heads of grain after him in whose sight I may find favor.” And she said to her, “Go, my daughter.”
Then she said, “Let me find favor in your sight, my lord; for you have comforted me, and have spoken kindly to your maidservant, though I am not like one of your maidservants.”