Fox News/screenshot
O'Reilly repeatedly told Trump that he was making a "big mistake" by skipping out on Fox's Thursday-night debate.
"You're running for president. I believe you want to improve the country. I believe that personally," the host told Trump.
He added: "You lose an opportunity to persuade people that you are a strong leader."
The real-estate mogul announced that he was refusing to participate in the Fox debate on Thursday, after a back and forth between himself and the network.
Trump repeatedly and loudly complained that one of the moderators will be Megyn Kelly, whom he has been attacking since August, when she was one of the moderators in the first Fox-hosted debate. At the time, Kelly angered Trump by questioning him about the disparaging comments he's made about women's appearances.
O'Reilly defended Kelly during his Trump interview.
"Kelly's question was within journalistic bounds," O'Reilly said after saying that he would have asked a similar question had he moderated the debate.
"In your Christian faith, there is a very significant tenet. And that's the tenet of forgiveness," O'Reilly later told Trump.
He added:
And I think you should forgive not only journalists who come at you in ways you don't like, but I think you should be the bigger man and say, 'You know what? I didn't like it. ... But I'm not going to take any action against it.' Don't you think that's the right thing to do?
Trump said he subscribed to a different tenet.
"It probably is. But it's called an 'eye for an eye,' I guess, also. You can look at it that way," he told O'Reilly.
"No, no, no, no," O'Reilly shot back. "If you're the Christian, the 'eye for the eye' rule goes out. Here's what it is: Turning the other cheek."
O'Reilly then tried appealing to Trump's patriotism, but also failed on that front.
"Come on! It's about the country!" he said.
Trump said that instead of doing the debate, he was hosting an event to benefit veterans on Thursday night. O'Reilly offered to team with Trump to host a larger event on behalf of veterans, but he did not appear to win over the mogul.
Later in the interview, O'Reilly asked Trump if he would "reconsider" his stance. Trump suggested that they had an agreement beforehand that he would not ask that question.
"Even though you and I had an agreement that you wouldn't ask me that, which we did … it's up to Fox," Trump said. "It's not up to me, Bill."
O'Reilly finished their exchange by complimenting Trump for coming onto the network for the interview despite his complaints about Fox. Trump said earlier that he wouldn't have done the interview, but he agreed last week to do it and didn't want to break his word.
"I don't know any politician under these circumstances," O'Reilly said, "that would've come on and did what you did here tonight."
Watch the first segment of the interview:
Additional reporting by Brett LoGiurato.