For the most part, when a politician takes their oath of office, they raise their right hand, place their left hand on the holy book of their choice, and swear to uphold the Constitution of the United States. Curiously, there's no constitutional requirement that an elected official take their oath of office on a holy book. In fact, John Quincy Adams allegedly took his oath of office on a book of laws, and Representative Kyrsten Sinema (D-AZ) the only member of Congress who lists her religion as "unaffiliated" took her oath on the Constitution.
But swearing on the Bible is still ubiquitous, especially among presidents, all of whom have been some form of Christian (plus JFK the Catholic). And lots of them, when they take the oath of office open the Bible to a passage that holds meeting to them. The practice has historical precedent, with George Washington taking his oath on an open page. Apparently, due to a bit of a rush, the book was opened to a random page, which means George Washington took the oath of office over Genesis 49:13 which reads:
"Zebulun shall dwell at the haven of the sea; and he shall be for an haven of ships; and his border shall be unto Zidon."
Inspiring stuff. The next time an inauguration had a confirmed open Bible was Abraham Lincoln's Second Inauguration, which appears to be confusingly opened to Matthew 7:1 (The famous "Judge not, that ye be not judged"), Matthew 18:7 and Revelations 16:7, verses that aren't gripping enough to bear repeating.
How did Lincoln have a bible open to three different passages? Probably using the same rhetorical and political skills that kept the Union together during and after a violent civil war. The world may never know.
With the hundreds and thousands of passages in the Bible, it's interesting to see which were repeated by multiple different people. Both Dwight D. Eisenhower and Ronald Regan used II Chronicles 7:14. Regan used the verse for both his inaugural elections, which states:
"If my people, which are called by my name, shall humble themselves, and pray, and seek my face, and turn from their wicked ways; then will I hear from heaven, and will forgive their sin, and will heal their land."
Franklin Roosevelt used the same passage for all four inagurations, I Corinthians 13, a passage most commonly used at weddings, and in the excellent 30 Rock episode:
"Love is patient and kind; love does not envy or boast; it is not arrogant or rude. It does not insist on its own way; it is not irritable or resentful; it does not rejoice at wrongdoing, but rejoices with the truth. Love bears all things, believes all things, hopes all things, endures all things."
Nixon twice opened his Bible to Isaiah 2:4, which states, among other things, "nation shall not lift up sword against nation, neither shall they learn war anymore." An ironic verse, given that Nixon presided over the bombing of Cambodia, but we can't all live up to the Bible verse we take the oath of office on.
I spent a lot of time Googling Bible quotes, and I think my favorite one is the Micah 6:8 chosen by both Jimmy Carter and Warren G. Harding which says:
"He hath shewed thee, O man, what is good; and what doth the Lord require of thee, but to do justly, and to love mercy, and to walk humbly with thy God?"
If our nation's leaders are going to take advice from a 2,000 year old book, that may be the best. One wonders why our presidents don't swear on the laws they're promising to uphold, but I think it's because everyone just wants to touch a famous Bible. And quite frankly, if that's the only chance I have to put my hand on Abraham Lincoln's Bible, I would take it.