Nothing in the Constitution requires any public official to swear an oath on the Bible, nor is that document based on “the God of the Holy Scriptures.” It is a charter for secular government.

U.S. Rep. Steve King also has a long history of promoting that movement’s pet ideas. In 2002, while a member of the Iowa legislature, King introduced a bill requiring that public schools teach that the United States derives its strength from 'Christianity, free enterprise capitalism and Western civilization.'

Sure, members of Congress can use a Bible to take the oath of office, but they’re not required to use anything. They can just take the oath if they choose. Or they can swear on another book.