WASHINGTON, D.C. — Joe Biden and Kamala Harris will take their oaths of office on Wednesday using Bibles that are laden with personal meaning, writing new chapters in a long-running American tradition — and one that appears nowhere in the law.

The Constitution does not require the use of a specific text for swearing-in ceremonies and specifies only the wording of the president’s oath. That wording does not include the phrase “so help me God,” but every modern president has appended it to their oaths and most have chosen symbolically significant Bibles for their inaugurations.

That includes Biden, who plans to use the same family Bible he has used twice when swearing in as vice president and seven times as senator from Delaware.

The book, several inches thick, and which his late son Beau also used when swearing in as Delaware attorney general, has been a “family heirloom” since 1893 and “every important date is in there,” Biden told late-night talk show host Stephen Colbert last month.

“Why is your Bible bigger than mine? Do you have more Jesus than I do?” quipped Colbert, who like Biden is a practicing Catholic.

Biden’s use of his family Bible underscores the prominent role his faith has played in his personal and professional lives — and will continue to do so as he becomes the second Catholic president in U.S. history.

He follows in a tradition of many other presidents who used family-owned scriptures to take their oaths, including Ronald Reagan and Franklin D. Roosevelt, according to the Joint Congressional Committee on Inaugural Ceremonies.

Some have had their Bibles opened to personally relevant passages during their ceremonies. Bill Clinton, for example, chose Isaiah 58:12 — which urges the devout to be a “repairer of the breach” — for his second inauguration after a first term marked by political schisms with conservatives.

Others took their oaths on closed Bibles, like John F. Kennedy, the first Catholic president, who in 1961 used his family’s century-old tome with a large cross on the front, similar to Biden’s.

The tradition of using a Bible dates as far back as the presidency itself, with the holy book used by George Washington later appearing on exhibit at the Smithsonian on loan from the Masonic lodge that provided it in 1789. Washington’s Bible was later used for the oaths by Warren G. Harding, Dwight D. Eisenhower, Jimmy Carter and George H.W. Bush.

But not every president has used a Bible. Theodore Roosevelt took his 1901 oath without one after the death of William McKinley, while John Quincy Adams used a law book in 1825, according to his own account.

Some have employed multiple Bibles during their ceremonies: Both Barack Obama and Donald Trump chose to use, along with others, the copy that Abraham Lincoln was sworn in on in 1861.

Harris plans to do the same for her vice-presidential oath, using a Bible owned by a close family friend and one that belonged to the late Supreme Court Justice Thurgood Marshall. Harris has spoken of her admiration of Marshall, a fellow Howard University graduate and trailblazer in government as the high court’s first African American justice.

“When I raise my right hand and take the oath of office tomorrow, I carry with me two heroes who’d speak up for the voiceless and help those in need,” Harris tweeted Tuesday, referring to Marshall and friend Regina Shelton, whose Bible she swore on when becoming attorney general of California and later senator.

Harris, who attended both Baptist and Hindu services as a child, worships in the Baptist faith as an adult.

While U.S. lawmakers have typically used Bibles for their oaths, some have chosen alternatives that reflect their religious diversity.

Democratic Rep. Keith Ellison of Minnesota, the first Muslim elected to Congress, in 2007 used a Quran that belonged to Thomas Jefferson, prompting objections from some Christian conservatives.

Jefferson’s Quran made a return in 2019 at the oath for Michigan Democratic Rep. Rashida Tlaib, one of the first two Muslim women elected to Congress.

Rep. Debbie Wasserman Schultz, D-Fla., chose a Hebrew Bible in 2005 to reflect her Jewish faith. Newly elected Georgia Democratic Sen. Jon Ossoff, who is also Jewish and who swears in Wednesday, plans to use Hebrew scripture belonging to Rabbi Jacob Rothschild, an ally of the Rev. Martin Luther King Jr. in the civil rights movement.

Former Rep. Tulsi Gabbard, D-Hawaii, opted for the Bhagavad Gita in 2013 after becoming the first Hindu elected to Congress.

And Sen. Kyrsten Sinema, D-Ariz., the only member of the current Congress who identifies as “religiously unaffiliated,” took her oath on the Constitution in 2018.