What is the symbolism of "a city upon a hill" in the novel, The Testaments: The Sequel to The Handmaid’s Tale?

The image of a city upon a hill symbolizes a nation that serves as an emblem of hope, an example for all other nations to emulate. Commander Judd borrows this phrase from Jesus' Sermon on the Mount to describe the kind of country the Sons of Jacob had in mind with Gilead. The phrase was also famously used by an early American Puritan named John Winthrop to describe the kind of country that was to become the United States, which in his vision was to serve a prime example of man's covenant with God; however, "a city upon a hill," is also an ironic symbol, in that such an elevated city would be visible for everyone to see, which means that any moral failings cannot be easily hidden from view.