Khizr Khan, whose soldier son died fighting in Iraq, addresses the Democratic National Convention in Philadelphia on Thursday with his wife by his side. (Michael Robinson Chavez/The Washington Post)

Khizr Khan, whose son died fighting in Iraq, said Sunday that Republican presidential nominee Donald Trump has a “black soul” that renders him unfit to lead the nation and that Senate Majority Leader Mitch McConnell (R) and House Speaker Paul Ryan (R) have a moral obligation to speak out against their party’s standard-bearer.

“He is a black soul. And this is totally unfit for the leadership of this beautiful country,” Khan said on CNN’s “State of the Union.” Khan said Trump does not have the temperament or moral character to be president and commander-in-chief.

“Two things are absolutely necessary in any leader or any person that aspires, wishes to be a leader. That is moral compass, and second is empathy. This candidate is void of both traits that are necessary for the stewardship of this country,” Khan said on CNN.

Speaking on NBC’s “Meet the Press,” Khan said the American political process is “wonderful” and “beautiful” and urged patriotic people not to vote for Trump.

“I implore those patriotic Americans that would probably vote for Donald Trump in November, I appeal to them not to vote for hatred, not to vote for fear mongering. Vote for unity. Vote for the goodness of this country. Vote for liberty and freedom. So, my appeal now is to the folks that are going to be thinking to vote for Trump,” Khan said.

Khan and his wife appeared last week at the Democratic National Convention, where Khan gave an emotional speech in which he questioned whether Trump had ever read the U.S. Constitution and offered to lend him his copy. The Khans’ son, Army Capt. Humayun Khan, was killed in Iraq in 2004.

Khizr Khan’s wife, Ghazala, did not speak on stage. The Khans are Muslim, and Trump questioned why Ghazala Khan did not speak. “She probably, maybe she wasn’t allowed to have anything to say,” he said.

In a subsequent interview, Ghazala Khan said she did not speak because she becomes overwhelmed with emotion when she sees her son’s picture (a large photo of Humayun Khan was displayed on the video screen on stage during her husband’s speech).

In an opinion piece published on the Washington Post’s website Sunday, Ghazala Khan responded directly to Trump..

“Donald Trump has asked why I did not speak at the Democratic convention. He said he would like to hear from me. Here is my answer to Donald Trump: Because without saying a thing, all the world, all America, felt my pain. I am a Gold Star mother. Whoever saw me felt me in their heart,” she wrote.

Ghazala Khan said Trump is “ignorant” when he talks about Islam. Trump has called for banning Muslims from entering the United States.

“If he studied the real Islam and Koran, all the ideas he gets from terrorists would change, because terrorism is a different religion.” she wrote. “Donald Trump said he has made a lot of sacrifices. He doesn’t know what the word sacrifice means.”

Khizr Khan defended his wife on Sunday, telling CNN that she is ill, has high blood pressure and cannot keep herself together when she sees images of her son.

“For this candidate for presidency to not be aware of the respect of a Gold Star mother standing there, and he had to take that shot at her, this is height of ignorance,” Khan said, referring to parents of troops who are killed serving their country.

“This country holds such a person in the highest regard. And he has no knowledge, no awareness. That is height of his ignorance. She is ill. She had high blood pressure. People that know her looked at her face, and she said, “I may fall off the stage,'” Khan, his voice quavering with emotion, said. “And I told her that you have to assemble yourself and stand for the beauty of this tribute that is being paid.”

In a tweet Sunday, Trump responded to Khan.

“I was viciously attacked by Mr. Khan at the Democratic Convention. Am I not allowed to respond? Hillary voted for the Iraq war, not me!” Trump wrote.

Khan said McConnell and Ryan must speak out against Trump.

It is their “moral, ethical obligation to not worry about the votes but repudiate him, withdraw the support. If they do not, I will continue to speak, and I am speaking,” Khan said.

In a statement released Saturday night, Trump called Humayun Khan a “hero” and accused Khizr Khan of saying “inaccurate things” about him at the convention.

In a tweet on Sunday morning, Trump said: “Captain Khan, killed 12 years ago, was a hero, but this is about RADICAL ISLAMIC TERROR and the weakness of our ‘leaders’ to eradicate it!”

In his CNN interview, Khizr Khan forcefully denounced Islamist terrorism.

“What he cites in the name of Islam and all that, that is not Islam at all. I wish he would have — somebody would have put something in his head that these are terrorists, these are criminals. These folks have nothing to do with Islam,” Khan said.

“Muslims hate this menace of terrorism as much as any other place. It is our duty to keep this country, our country, beautiful country, safe,” he said.