Washington ( CNN ) -- At his request , President Barack Obama is ending his inaugural oath with : `` So help me God . '' Those four words are not legally or constitutionally required , unlike other federal oaths that invoke them as standard procedure . Historians have wrangled over whether George Washington established precedent by adding the phrase on his own during his first Inaugural acceptance , but the Library of Congress website states he did . Abraham Lincoln was reported to have said it spontaneously in 1861 and other presidents over the years have followed suit . A Bible is traditionally used in administering the oath . Opinion : Presidents should not swear in on a Bible . Obama took the official oath on Sunday at the White House with his left hand on the family Bible of his wife , Michelle . At Monday 's ceremonial swearing-in at the Capitol , he will use Bibles from Lincoln and Martin Luther King Jr. Obama took the oath with the same Lincoln Bible in 2009 when he made history as the first African-American president . The Constitution lays out the exact language to be used in the oath : `` I do solemnly swear ( or affirm ) that I will faithfully execute the Office of President of the United States , and will to the best of my Ability , preserve , protect and defend the Constitution of the United States . '' Four years ago , a California atheist , Michael Newdow , objected and went to federal court to prevent Chief Justice John Roberts from prompting the president-elect to repeat the `` so help me God phrase . '' Newdow , along with several non-religious groups , argued the words violate the constitutional ban on government `` endorsement '' of religion . The high court ultimately rejected the lawsuit two years ago , and no such legal challenges are expected this time . Lyndon Johnson 's 1965 swearing-in marked a change from tradition . His wife Claudia , known better as Lady Bird , held the Bible , a job previously managed by the high court 's clerk . Spouses have since had the honor . 13 reasons to follow the inauguration on CNN 's platforms and nowhere else . CNN 's Kevin Liptak contributed to this report .
Obama used family members at Sunday 's swearing - in ; Will used two relatives on Monday . ' So help me God ' not a part of presidential oath , but has been said . Legal challenge cut short before 2009 inauguration .