President Trump told a crowd of college graduates Saturday they should not be afraid to challenge the establishment or government elites who would second-guess whatever they do.

"Following your convictions means you must be willing to face criticism from those who lack the same courage," Trump said during a commencement speech at Liberty University in Lynchburg, Va., capping a week in which his dismissal of FBI Director James Comey roiled the Washington political and legal systems.

"We don't need a lecture from Washington to us on how to lead our lives," Trump said at another point.

Facebook video: President Trump speaks to graduates at Liberty

Trump did not specifically mention Comey or other political disputes that have marked his first four months in office, but made repeated general references to his maverick campaign and presidency.

At one point, Trump said he has seen firsthand how "the system is broken." At another, he told students and parents at the conservative religious school that "nothing is easier or more pathetic than being a critic."

Trump also praised the military for its battle against the Islamic State and referred at one point to his recent executive order on religious freedom.

He also engaged in more traditional commencement rhetoric, congratulating the graduates on their accomplishments and lauding the school's academic credentials and football program. Speaking at a school that bills itself as the world's largest Christian university, Trump praised the Liberty graduates for their political activism, and he cited the large support of religious conservatives for his campaign.

"What will you give back to this country and indeed to the world?" Trump asked the graduates.

Earlier, during the Air Force One ride to southwestern Virginia, Trump told reporters that "we can make a fast decision" on a new FBI director, possibly before his departure Friday on a trip to the Middle East and Europe. Trump said he and his staff are looking at "very well known, highly respected, really talented people, and that's what we want for the FBI."

The search takes place amid an ongoing firestorm over Trump's dismissal of Comey and new questions over whether he taped conversations with the now-former FBI director.

In a Friday tweet, Trump said Comey "better hope that there are no 'tapes' of our conversations before he starts leaking to the press!"

Since that comment, neither Trump nor aides would confirm or deny questions about whether he in fact tapes conversations.

"I won't talk about that," Trump told Fox News in an interview. "All I want is for Comey to be honest and I hope he will be and I'm sure he will be, I hope."

Democrats, and some FBI officials, charge Trump got rid of Comey in order to impede an investigation into possible collusion between Trump campaign officials and Russia, which tried to influence the 2016 election by hacking prominent Democrats.

Trump, angry over media coverage over the Comey issue, has also threatened to end White House news briefings.

In a commencement address of her own, U.S. Sen. Elizabeth Warren, D-Mass, told University of Massachusetts-Amherst graduates they should fight for “the principle that no one, no one in this country is above the law and we need a Justice Department, not an obstruction of justice department.”

Trump has denounced the Russian investigation as a "hoax" and "witch hunt."

During the commencement address at Liberty's football stadium, Trump told the graduates they should keep going and "never quit" in face of adversity. At one point, he said, "you aren't going to let other people tell you what you believe, especially when you know that you're right."

Describing the supportive crowd as "Champions for Christ," he encouraged them to get involved in public life.

"There may very well be a president or two in our midst," Trump said.