Donald Trump. Spencer Platt/Getty Images Donald Trump took a swipe at Hillary Clinton on Wednesday for her early September health episode outside a 9/11 memorial event, mocking the Democratic nominee for not being able to "make it to her car."

"You see all the days off that Hillary takes?" Trump asked the crowd at an Iowa rally. "Day off. Day off. Day off. All those day offs. And then she can't even make it to her car."

"Isn't that tough?" he continued. "All those day offs. Right. Boom. Every see her chart? 'She won't be campaigning today. She won't be campaigning today.'"

Trump was referencing an early-September incident when Clinton appeared to collapse outside of her car at the 9/11 memorial in New York. Her campaign later disclosed that she had a pneumonia, and she took part of the following week off the campaign trail.

Trump was initially reluctant to comment on the episode, wishing her a speedy recovery. But Trump hinted at the incident later in the week. However, Wednesday's comment was one of his strongest jabs at the moment yet.

During Monday's debate, Trump and Clinton had a lengthy back-and-forth over his accusation that she doesn't "have the stamina" to be president.

"She doesn't have the look — She doesn't have the stamina," Trump said when debate moderator Lester Holt asked him about his prior statement that Clinton doesn't have "the presidential look." "I said she doesn't have the stamina. And I don't believe she does have the stamina. To be president of this country, you need tremendous stamina."

"You have to be able to negotiate our trade deals," he continued. "You have to be able to negotiate, that's right, with Japan, with Saudi Arabia. I mean, can you imagine, we're defending Saudi Arabia? And with all of the money they have, we're defending them, and they're not paying? All you have to do is speak to them. Wait. You have so many different things you have to be able to do, and I don't believe that Hillary has the stamina."

Clinton fired back, mentioning her past experiences.

"Well, as soon as he travels to 112 countries and negotiates a peace deal, a cease-fire, a release of dissidents, an opening of new opportunities in nations around the world, or even spends 11 hours testifying in front of a congressional committee, he can talk to me about stamina," she said to applause from the crowd.

"The world — let me tell you," Trump responded. "Let me tell you. Hillary has experience, but it's bad experience. We have made so many bad deals during the last -- so she's got experience, that I agree."