Fear and foreigners
The Old Testament book of Ezra tells of events when Jewish exiles in Babylon were permitted to return to Israel and begin rebuilding Jerusalem. Prophets had spoken of a day when exiles returned and Jerusalem became great again, surpassing the glory of David and Solomon. But it didn't work out quite that way. Jerusalem remained a shell of its former self, an insignificant, backwater town.
Naturally there were people who looked for something or someone to blame. Perhaps they weren't pure enough to please God, and some began to look with suspicion on those who had married "foreign wives." (In the companion book of Nehemiah, 13:1 cites Deuteronomy 23:3–6 and its ban on Moabites and Ammonites from the assembly of Yahweh.) Eventually Ezra orders the people, "Separate yourselves from the peoples of the land and from the foreign wives." That likely would be a death sentence to many women and children, but God demands purity.
Interestingly, the Old Testament has another book that takes an entirely different point of view. The title character in the book of Ruth is a Moabite, and the great-grandmother of King David no less. If Ezra's rule had been enforced in her time, David might never have existed. The story of Ruth lifts up a Moabite woman as a paragon of virtue and faithfulness. She is a "foreign wife" like those Ezra banishes in the name of the purity God demands.
