Controversy is raging around President Trump's executive order on immigration. Critics say it's divisive. Trump supporters want opponents to calm down.
It's another example of a divided America.
"There's a lot of fear, I hear it every day," Boston Mayor Marty Walsh said, according to CBS and The Associated Press. "There's a lot of fear and there's a lot of anger."
"There are folks who like what Trump is saying but not fully understanding what he means by it, so it's really I think dividing," Walsh continued. "We should be uniting the country not dividing the country."
New York Times bestselling author Philip Yancey believes the division is not just limited to the U.S., and he points to a new book -- not his own -- as inspiration during troubling times.
He's referring to Rod Gragg's My Brother's Keeper: Christians Who Risked All to Protect Jewish Targets of the Nazi Holocaust.
"At a time when fear and divisiveness are resurging around the globe, we badly need this harrowing account of unsung heroes who risked all for the sake of good," Yancey said.
In the book, Gragg, an award-winning historian, documents stories of Christians who put their lives on the line to help Jews during the Holocaust. The book chronicles how some even paid the ultimate sacrifice to protect Jewish men, women and children from the Nazis.
RELATED: Abigail Robertson talked with Rod Gragg for a CBN News Facebook Live Monday. He's the author of “My Brother’s Keeper: Christians who Risked All to Protect Jewish Targets of the Nazi Holocaust”
The nation of Israel has recognized these Christians as "Among the Righteous of the Nations."
Publisher's Weekly calls the work "an inspiring look at 30 Christian heroes" who displayed "mind-boggling bravery" by not turning a blind eye to the evils of the Holocaust.