Donald Trump will be held to these 35 (or 39) words for the length of his presidency

When Donald Trump is sworn in as the 45th president of the United States on Friday, he’ll take the oath of office, which is outlined in the constitution, has been said or affirmed by every single president who has held office since George Washington in 1789.

These are the words, according to the Museum of American History:

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.

Tweet This Click to share quote on Twitter: <em>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.</em>

Global News will have live coverage of Donald Trump’s inauguration throughout the day Friday. Trump will stand up and say these words in front of thousands of people at noon on Jan. 20.

READ MORE: Will Canadians be watching Donald Trump’s inauguration celebrations?

The oath will be administered by U.S. Supreme Court Chief Justice John Roberts.

Roberts also swore in President Barack Obama in 2008, but it didn’t go so well.

They fumbled over the words of the oath during the public inauguration, and had to repeat the ceremony in the White House map room the next day.

Though Obama was officially president after the first ceremony, the repeat was done just to be cautious, officials said.

The oath is 35 words long but some presidents make it 39 by tacking on “so help me God.”

There are conflicting stories about when the ad lib started.

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Some say George Washington added the words when he took the oath at his 1789 inaugural, but others say the first eyewitness account of a president using those words came at Chester Arthur’s inauguration in 1881.

WATCH: Donald Trump arrives in Washington, prepares to be sworn in as president. Jackson Proskow reports.

2:00 Donald Trump arrives in Washington, prepares to be sworn in as president

Historian Jim Bendat says Washington’s use of the phrase is a myth, but every president since 1933 has done it.

Vice president-elect Mike Pence will be sworn in directly before Trump, and his oath is actually longer than the president’s.

Pence will say these words:

I do solemnly swear (or affirm) that I will support and defend the Constitution of the United States against all enemies, foreign and domestic; that I will bear true faith and allegiance to the same; that I take this obligation freely, without any mental reservation or purpose of evasion; and that I will well and faithfully discharge the duties of the office on which I am about to enter: So help me God.

Tweet This Click to share quote on Twitter: <em>I do solemnly swear (or affirm) that I will support and defend the Constitution of the United States against all enemies, foreign and domestic; that I will bear true faith and allegiance to the same; that I take this obligation freely, without any mental reservation or purpose of evasion; and that I will well and faithfully discharge the duties of the office on which I am about to enter: So help me God. </em>

Pence will be sworn in by Supreme Court justice Clarence Thomas – which marks the first time an African American will swear in a vice president, according to the Presidential Inauguration Committee.

WATCH: Predicting the tone Donald Trump will take after being sworn in. Ines de La Cuetara reports.

2:12 Predicting the tone Donald Trump will take after being sworn in