The tradition of using a Bible during the swearing-in goes back to the very first inauguration, but not all Presidents have used one.

There are so many traditions on Inauguration Day, but only one is required by law, and that is saying the Oath of Office. Taking the Oath with your hand on a book According to the U.S. Department of State,

There’s a unique family backstory behind the holy book that the President-elect will use for his second inauguration on Monday.