Nothing in the Constitution or laws of the United States requires office-holders to swear on a Bible, or any other book.Roy Moore campaign spokesman responds with silence when asked if he knew people can be sworn in with a text other than the Christian bible pic.twitter.com/B65qIKBjlI— The Lead CNN (@TheLeadCNN) December 12, 2017
In Congress, some use Bibles, and some do not. From CRS:
The first order of business in a new Senate is the swearing-in of Senators elected or reelected in the most recent general election and of newly appointed Senators. On occasion in recent years, the majority leader or the majority and minority leaders might first be recognized for brief remarks. If there is a contested or undecided Senate election, the leadership might provide a status report and plan for its resolution, before or after Senators are sworn in.
After the Vice President lays the certificates of election and appointment before the Senate and states that their reading will be waived if there is no objection, he calls those Senators to the front of the chamber, generally in alphabetical order in groups of four, to take the oath and to also “subscribe to the oath” in the official oath book. Each Senator may be accompanied by the other Senator from his or her state, the Senator he or she is replacing, or a former Senator.
The oath, which is the same for Representatives and executive and judicial appointees, is as follows:I do solemnly swear (or affirm) that I will support and defend the Constitution of the United States against all enemies, foreign and domestic; that I will bear true faith and allegiance to the same; that I take this bligation freely, without any mental reservation or purpose of evasion; and that I will well and faithfully discharge the duties of the office on which I am about to enter. So help me God.An oath is mandated by Article VI of the Constitution; its text is set by statute (5 U.S.C. 3331).
When Senators take the oath, they raise their right hand to swear or affirm, repeating after the Vice President. Many Senators hold a family Bible or another item, and some hold nothing. There is no requirement that a Bible or anything else be used when the oath is taken.
When the Vice President (or another individual of a Senator’s choosing) and individual Senators subsequently reenact the swearing-ins in the Old Senate Chamber with the Senator’s family, each Senator might hold a Bible, another item, or nothing in his or her left hand. Although photography is not permitted on the Senate floor, photographers are present for the ceremonial swearing-in. Individuals might also record a ceremonial swearing-in.CRS describes the House procedure:
After taking the oath, the Speaker administers the oath to all Members of the House, en masse, including the nonvoting Delegates and Resident Commissioner. The Speaker directs the Representatives-elect to rise and raise their right hands...As the Members-elect raise their right hands, they are not required to hold anything in their left hands. Many have held a family Bible or another sacred text in their left hands, but there is no requirement that anything be held when the oath is taken.
The same is true for Representatives who re-enact the event with their families and the Speaker in the Speaker’s office after the formal ceremony. Many Members choose to hold something meaningful in their left hands. These objects have often been, but are not limited to, a family heirloom or something else of special significance. Nothing, however, is required.