For generations, young Christians have learned how to hold and respect their Bibles during competitions known as "Sword drills."
The sword image comes from a New Testament affirmation that the "word of God is … sharper than any two-edged sword."
Drill leaders say, "Attention!" Competitors stand straight, hands at their sides.
"Draw swords!" They raise their Bibles to waist level, hands flat on the front and back covers. The leader challenges participants to find a specific passage or a hero or theme in scripture.
"Charge!" Competitors have 20 seconds to complete their task and step forward. For some, four or five seconds will be enough.
The key is knowing how to open the Bible, as well as hold it.
It's safe to say the young Donald Trump didn't take part in many Bible drills while preparing to be confirmed, at age 13 or thereabouts, as a Presbyterian in Queens, New York City. His mother gave him a Revised Standard Version -- embraced by mainline Protestants, shunned by evangelicals -- several years earlier.
President Trump was holding a Revised Standard Version during his iconic visit to the historic St. John's Episcopal Church, after police and security personnel drove protesters from Lafayette Square, next to the White House. To this day, evangelicals favor other Bible translations, while liberal Protestants have embraced the more gender-neutral New Revised Standard Version.
A reporter asked: "Is that your Bible?"
The president responded: "It's a Bible."
"Trump is a mainline Protestant. That's what is in his bones -- not evangelicalism. It's clear that he's not at home with evangelicals. That's not his culture, unless he's talking about politics," said historian Thomas S. Kidd of Baylor University, author of "Who Is an Evangelical? The History of a Movement in Crisis."
The scene at St. John's Episcopal was "another example of Trump not knowing what was appropriate. … It was like he was saying, 'I'm going to hold up a Bible and that means God is on our side.' He's a mainline Protestant acting the way that he thinks an evangelical would act," said Kidd, reached by telephone.
A few core pro-Trump evangelicals hailed his gesture as a symbol of strength and leadership, while liberal Protestants -- such as clergy linked to St. John's -- made it clear they were offended.
"Had the president opened the Bible he was holding, he could have read passages calling on us to love God and our neighbor, to seek God in the face of strangers and even to love our enemies," noted Bishop Mariann Edgar Budde of the Episcopal Diocese of Washington, writing in The New York Times.
Meanwhile, Whitney T. Kuniholm, senior vice president of the American Bible Society, issued a statement opposing the use of "the Bible as a political symbol, one more prop in a noisy news cycle."
A patriarch of the old Religious Right, the Rev. Pat Robertson, proclaimed on a 700 Club broadcast: "It seems like now is the time to say, 'I understand your pain, I want to comfort you, I think it's time we love each other.' But the President took a different course. He said, 'I am the "president of law and order,' and he issued a heads-up."
There is nothing new about presidents with Bibles. In recent decades, Jimmy Carter taught Bible classes, George W. Bush testified about his Bible-based alcohol recovery program and Barack Obama read Psalm 46 at the rite marking the 10th anniversary of 9/11. Bill Clinton waved a Bible -- during a sex scandal -- at camera crews while leaving Hillary Clinton's home church.
Through all of that, and much more, Americans watched evangelist Billy Graham hold a Bible high in one hand while exclaiming, "The Bible says!" To this day, some evangelicals refer to gripping a Bible in that manner, with one cover curled under, as "Billy Graham-ing" -- a verb -- the Good Book.
"When Graham was holding a Bible in his hand it was always a symbol of the authority of scripture," said Kidd. "That Bible was always open, and Billy was saying, 'We all know this is the Word of God. Pay attention.' What mattered was what the Bible was saying to us. … I'm not sure that many Americans can agree, these days, on what the Bible is saying about the issues that divide us."