>It's a serious question….
There is no requirement that a Bible be used to take the oath of office.
Article VI, Clause 3 of the Constitution states that: "no religious Test shall ever be required as a Qualification to any Office or public Trust under the United States." Additionally, the Constitution provides flexibility by allowing officials to either "swear" or "affirm" their oath, accommodating those whose religious beliefs prevent them from swearing oaths.
While most U.S. presidents have used a Bible during their inauguration, a few have not.
John Quincy Adams chose to place his hand on a book of constitutional law, believing it better represented the secular nature of his duties.
Thomas Jefferson did not use a Bible.
Theodore Roosevelt did not use any book during his first swearing-in following William McKinley's assassination.
Calvin Coolidge, in keeping with his Puritan roots, did not use a Bible, although one was nearby.
Lyndon Johnson, sworn in on Air Force One after the assassination of John F. Kennedy, used a Missal (Catholic liturgical book) found in the plane's bedroom.
https://www.rocketcitynow.com/article/news/nation-world/do-you-have-to-use-a-bible-to-take-the-oath-of-office/525-9860ec72-6412-47e3-aff1-835860f28e43
Article VI Supreme Law
Clause 3 Oaths of Office
The Senators and Representatives before mentioned, and the Members of the several State Legislatures, and all executive and judicial Officers, both of the United States and of the several States, shall be bound by Oath or Affirmation, to support this Constitution; but no religious Test shall ever be required as a Qualification to any Office or public Trust under the United States.
https://constitution.congress.gov/browse/article-6/clause-3/