Trump, who was misrepresenting comments Omar made in a 2013 interview, has repeatedly criticized Omar, one of two Muslim women serving in Congress, and used her words to attack her and other Democrats.
Here’s the context around his comments today, and what the Minnesota Democrat has said in the past.
WHAT TRUMP SAID: On Monday, Trump continued to criticize Omar and the other Democratic congresswomen.
"I look at Omar. I don't know, I never met her. I hear the way she talks about al Qaeda. Al Qaeda has killed many Americans. She said you can hold your chest out, you can, 'when I think of al Qaeda I can hold my chest out.'
WHAT REP. OMAR SAID ABOUT AL QAEDA: In 2013, Omar, then a political activist, appeared on a local Twin Cities current affairs program, "BelAhdan," after the bombing of a Kenyan shopping mall by terror group al-Shabab.
In conversations about how American Muslim communities navigate responding to terror attacks committed by Muslim extremists, the host, Ahmed Tharwat, noted how Arabic names for groups like al Qaeda, Hezbollah and al-Shabab are commonly used in the U.S.
"It's very interesting that we keep the Arabic name to such a violent, or negative entity," he said.
"They don't mean anything evil," Omar replied, calling their usage "a product of the sensationalized media"
"You have these soundbites and you have these words and everybody says it with such intensity that it must hold meaning," she said.
As an example, she described how one of her professors in a college course on terrorism used to pronounce al Qaeda.
"The interesting thing about the class was that every time the professor said 'al Qaeda,' his shoulders went up," she said.
A clip of Omar's comments has circulated on conservative media and social media, which likely prompted the president's comments.
Asked to respond to Trump’s comments about her previous remarks on Monday, Omar said it was "beyond time to ask Muslims to condemn terrorists."
The Sept. 11 attacks
WHAT TRUMP SAID: Trump also took aim at comments Omar made earlier this year about the September 11th attacks.
"When she talked about the World Trade Center being knocked down, 'some people,' you remember the famous 'some people.' These are people who in my opinion hate our country," Trump said.
WHAT OMAR SAID ABOUT 9/11: Speaking at a Council on American-Islamic Relations event in March, Omar said the advocacy group "was founded after 9/11, because they recognized that some people did something and that all of us were starting to lose access to our civil liberties."
The president and Republicans have accused her of trivializing the Sept. 11 attacks with her remarks. Omar has said she was taken out of context.
In her speech after the Christchurch mosque shootings in New Zealand, Omar urged Muslims to stand up for themselves and advocate for their rights as the advocacy group has done.
"Many people expect our community to feel like it needs to hide every time something happens," she said in the speech. "But repeatedly, we have shown them that we are not to be bullied, not to be threatened, we are not to be terrorized, we are strong and resilient, and we will always show up to be ourselves because we know we have a right to a dignified existence and a dignified life."
(Note: CAIR was actually established in 1994, not in 2001, as Omar claimed.)
Attacks on Israel
Omar, along with Rep. Rashida Tlaib, D-Mich., the only other Muslim woman in Congress, have been criticized by Republicans and Democrats for comments about the Israeli government and the influence of pro-Israel lobbyists in Washington, and accused them of evoking anti-Semitic tropes.
Trump has used their comments to claim that Democrats hate Jews, a conflation critics and some Democrats consider to be anti-Semitic, given that American Jews have increasingly criticized the Israeli government in recent years.
Omar has apologized for some of her comments, but defended her criticism of the Israeli government.
WHAT OMAR SAID: In January, Omar was criticized for a (deleted) 2012 tweet where she said Israel "has hypnotized the world, may Allah awaken the people and help them see the evil doings of Israel," after the 2012 conflict with Hamas in Gaza. She defended the comments, saying she was criticizing the military action by Israel.
In February, Omar responded on Twitter to a report that Republicans wanted her punished for criticism of Israel, tweeting "It's all about the Benjamin's baby," appearing to be using a common way of referring to $100 bills – which feature Benjamin Franklin – or even playing off a line from “It’s All About the Benjamins,” a 1997 song from rapper Sean "Puff Daddy" Combs that critics said also evoked stereotypes about Jews and money.
Omar followed up with another tweet mentioned the American Israel Public Affairs Committee, the prominent pro-Israel advocacy group that wields significant influence in Washington among both political parties.
She eventually apologized for touching on the "painful history of anti-Semitic tropes."
A few weeks later, Omar was at a progressive event in Washington where she said pro-Israel activists pushed "allegiance to a foreign country," in an effort to clarify her initial comments.
"I want to talk about the political influence in this country that says it is OK for people to push for allegiance to a foreign country," Omar said, immediately prompting criticism that she was evoking stereotypes about "dual loyalty," a trope seen as anti-Semitic but also associated historically with other immigrant groups.
In March, the House passed a resolution condemning anti-Semitism, racism and bigotry in response to Omar's comments, though some Democrats were angry that it didn't mention the congresswoman by name.