During President Obama’s swearing-in in 2009, Michelle Obama held the Bible used by Abraham Lincoln at his inauguration in 1861. (Dennis Brack/Bloomberg News)

Martin Luther King Jr. carried a black leather King James Bible on his journeys as a young pastor starting out in Montgomery, Ala. He turned to this “traveling Bible” for inspiration, his family says, as he fought for freedom and equality.

President Obama will put his hand over King’s well-worn Bible at his public swearing-in at the U.S. Capitol on Jan. 21, the holiday celebrating the birthday of the slain civil rights leader. King’s Bible will be stacked with the burgundy velvet and gilded Bible used by President Abraham Lincoln at his first inauguration.

Obama chose the Lincoln Bible for his inauguration in 2009, making him the first president to do so since it was initially used in 1861. President Harry S. Truman also used two Bibles, as did Dwight D. Eisenhower and Richard M. Nixon.

The announcement about the Bibles, to be made publicly Thursday, is part of the slow unspooling of inaugural details that fascinates lovers of ceremonial Americana.

Presidential inaugurations have become more filled with rites, and such decisions are especially weighty now at a time when the White House is aware that Americans are struggling to come together.

King’s family said in a statement that he would be “deeply moved” to see Obama use the traveling Bible on Martin Luther King Jr. Day, “and we hope it can be a source of strength for the President as he begins his second term.”

“With the Inauguration less than two weeks away, we join Americans across the country in embracing this opportunity to celebrate how far we have come, honor the legacy of Martin Luther King Jr. through service, and rededicate ourselves to the work ahead,” the statement added.

According to the Presidential Inaugural Committee, which organizes the swearing-in ceremony, King traveled with various books, including this Bible. “It was used for inspiration and preparing sermons and speeches, including during Dr. King’s time as pastor of Dexter Avenue Baptist Church” in Montgomery, the committee said in a statement.

Obama and Vice President Biden will be sworn in privately on Sunday, Jan. 20 — the date required by the Constitution. For that first ceremony, Obama will use the family Bible of his wife’s family. According to the inaugural committee, that Bible “was a gift from the First Lady’s father, Fraser Robinson III, to his mother, LaVaughn Delores Robinson, on Mother’s Day in 1958. Mrs. Robinson was the first African-American woman manager of a Moody Bible Institute’s bookstore.” That Bible was the only one Michelle Obama’s grandmother used after that, a committee statement said.

For both the private and then the Monday public ceremonies, Biden will be sworn in with a Bible that has been in his family since 1893: a five-inch-thick volume with a Celtic cross on the cover. He also used it for his swearings-in as a U.S. senator and in 2009 as vice president.

Some aspects of the inaugural ceremony have changed slightly over the decades. Having official prayers offered dates only to the 1930s, historians say. But presidents have used Bibles to be sworn in since George Washington, even though the Constitution does not require it. The Constitution also does not require the phrase “So help me God” at the end, but that has become standard, said Donald Ritchie, the historian of the U.S. Senate.

He also noted that the image of the president’s spouse holding the Bible dates only to Lady Bird Johnson doing so in 1965.

Chief justices of the Supreme Court now traditionally deliver the oath, but Ritchie said any federal official can do so.

Several non-Christian members of Congress have recently used other scriptures, including Rep. Keith Ellison, the first Muslim elected to Congress, in 2007. The Minnesota Democrat used a Koran owned by Thomas Jefferson.

Obama veered from tradition in one key aspect of the ceremony: He invited Myrlie Evers-Williams, widow of slain civil rights figure Medgar Evers, to deliver the invocation prayer. It will be the first time a woman, and a layperson rather than clergy, has done so.