Religious rituals have been practiced for years at presidential inaugural ceremonies as a natural part of the American political tradition.
Since the establishment of the country, US presidents were seen as one of the most important representatives of social and religious values.
Joe Biden took his post Wednesday by reciting the oath of office in a heavily-guarded but sparsely attended ceremony at the US Capitol.
Before the ceremony, Biden, the second Catholic president, attended mass with then-incoming Vice President Kamala Harris at the Cathedral of St. Matthew the Apostle -- where the funeral for John F. Kennedy, the nation's first Catholic leader, was held in 1963.
Several presidents have chosen St. John's Episcopal Church, also known as the "Church of the Presidents," for their inaugural day service, including Donald Trump, Barack Obama and George W. Bush.
In every swearing-in ceremony, a priest prays and wishes the new US president well before taking the oath of office.
For Biden, Catholic priest Leo J. O'Donovan delivered the prayer. The full prayer is as follows:
Gracious and merciful God, at this sacred time we come before you in need, indeed on our knees.
But we come still more with hope, and with our eyes raised anew to the vision of a more perfect union in our land - a union of all our citizens to promote the general welfare and secure the blessings of liberty to ourselves and our posterity.
We are a people of many races, creeds, and colors, national backgrounds, cultures, and styles, now far more numerous and our land much vaster than when Archbishop John Carroll wrote his prayer for the inauguration of George Washington 232 years ago.
Archbishop Carroll prayed that you, O Creator of All, would assist with your spirit of 'holy counsel and fortitude, the president of these United States, that his administration might be conducted in righteousness and be eminently useful to your people.'
Today we confess our past failures to live according to our vision of equality, inclusion, and freedom for all.
Yet we resolutely commit still more now to renewing the vision, to caring for one another in word and deed, especially the least fortunate among us, and so becoming a light for the world.
There is a power in each and every one of us that lives by turning to every other one of us - a thrust of the Spirit to cherish and care and stand by others and above all those most in need. It is called love and its path is to give ever more of itself.
Today it is called American patriotism, born not of power and privilege, but of care for the common good with malice toward none and with charity for all.
For our new president, we beg of you the wisdom Solomon sought when he knelt before you and prayed for an understanding heart so that I can govern your people and know the difference between right and wrong.
We trust in the counsel of the letter of James: "If any of you lacks wisdom you should ask God who gives generously to all without finding fault and it will be given to you."
Pope Francis has reminded us how important it is to dream together. "By ourselves," he wrote, "we risk seeing mirages, things that are not there. Dreams, on the other hand, are built together."
Be with us, Holy Mystery of Love, as we dream together.
Help us under our new president to reconcile the people of our land, restore our dream, and invest it with peace and justice and the joy that is the overflow of love.
To the glory of your name forever. Amen.
Biden was sworn in on a bible that belongs to his family for nearly 130 years, continuing a tradition he has kept during his long political career.
He put his left hand on the five-inch thick bible that featured a Celtic cross on the cover that was held by now-first lady Jill Biden and took the 35-word oath administered by Chief Justice John Roberts.
Biden first used it during his first Senate swearing-in in 1973. Since then, he has used it whenever he takes an oath of office, including his swearing-in as vice president in 2009 and 2013.
The heirloom was also used by Biden's son, Beau, when he was sworn in as Delaware Attorney General in 2007.
By convention, incoming presidents raise their right hands and place the left on a bible while taking the oath of office.
Although no law requires the president to say "So help me God" at the end of the oath or use the bible, both have been used in many inauguration ceremonies. The debate about which president first used "So help me God" continues while some say George Washington, others point to Chester A. Arthur as the founding father of the tradition.
The majority of a president's first address following their oaths refer to religious elements and the bible.
Basing his speech on "unity," Biden said "to restore the soul and secure the future of America requires so much more than words," and "it requires the most elusive of all things in a democracy, unity. Unity."
He also cited St. Augustine to emphasize the importance of unity.
"Many centuries ago, St. Augustine, a saint in my Church, wrote that a people was a multitude defined by the common objects of their love," said Biden.
These "common objects" that define Americans, he said, are "opportunity, security, liberty, dignity, respect, honor and, yes, the truth."
Biden also participated in a virtual inauguration prayer service Thursday.
The traditional prayer normally takes place at Washington National Cathedral with representatives of different religions and beliefs, but due to the coronavirus pandemic, the event was virtual.
