(CNN)The 116th class of Congress is one of the most diverse to serve the United States -- and nowhere is that more evident than in this viral photo showing the books used during Thursday's swearing-in ceremonies.
Muslim and Jewish holy books among many used to swear-in Congress
More than a dozen documents and books -- including the US Constitution, Eastern Orthodox Bible and Quran -- were used to swear in officials of various ethnic and religious backgrounds.
Among them were Ilhan Omar and Rashida Tlaib, the first two Muslim women to serve in the House of Representatives.
Tlaib, a Michigan Democrat, also made history as the first Palestinian-American woman to serve in Congress. Tlaib said she was considering using Thomas Jefferson's centuries-old Quran during the ceremony, calling the holy book a symbol that "Islam has been part of American history for a long time."
Although Capitol Hill is still largely dominated by Christians, religious diversity is growing.
Nearly nine in 10 members of Congress (88%) identify as Christians, according to a recent Pew study. Two of the 253 Republicans do not identify as Christian: Reps. Lee Zeldin and David Kustoff, who are Jewish.
Among Democrats, 61 of the 281 party members do not identify as Christian.
About half of those are Jewish, 18 declined to name a religious affiliation, three are Muslim, three are Hindu, two are Buddhists, two are Unitarian Universalists and one is not affiliated with a particular religion.
Rep. Madeleine Dean from Pennsylvania took her oath on her uncle's Bible.
"I am honored to be sworn in on my Uncle Walter Dean's Bible," she posted on Twitter. "He worked as a Priest for 53 years, but he was also an educator. He always believed in me and inspired my passion for learning, teaching, and service."
Senators and representatives can take oaths of office on any book they desire. According to the US Constitution, they are only bound "by oath or affirmation" to support the Constitution and no religious test is required as a qualification for office.