Rep.-elect Keith Ellison, D-Minn., the first Muslim-American elected to the U.S. Congress, is opting not to take his oath of office on the Bible on Jan. 3, instead wanting to pledge his loyalty to the U.S. and its Constitution on a Koran.

That has one conservative, radio talk show host Dennis Prager, up in arms.

"It has nothing to do with his being a Muslim, it has to do with the fact that it's not the Bible," Prager told FOX News. "If a Mormon-American decided to substitute the Book of Mormon for the Bible, I would have the same problem. If a scientologist wanted L. Ron Hubbard's 'Dyanetics' to be the book, I would have a problem."

Prager says the Bible is the most important book in American history and that's why it should be used.

"George Washington began this movement. He was the one to bring a Bible and swear on it. Every president except one, Teddy Roosevelt, because it was right after the assassination of James McKinley and they didn't have time for a Bible. And every president has done this," Prager said, adding that congressional members have followed the tradition.

Of course, Praeger's anger may be misplaced, said a spokesman for Ellison. The Koran is only being used for the ceremonial swearing-in, since the official swearing-in does not require any Bibles to be used.

During the official ceremony, all members of Congress take the oath at the same time on the House floor. Traditionally, the mass oath has the representatives standing with their right hands raised for a joint oath of office.

Later in the day, the tradition is for new members, and even many re-elected members, to have their pictures taken with family by their side. At that time, the House speaker or a family member stands across from the representative holding the individuals' personal book for the photo-op.

FOX News' Molly Hooper and Jim Mills contributed to this report.