Donald Trump and some pyramids. Composite. (Trump: REUTERS/Rick Wilking. Background: Mabdalla/Wikimedia Commons) Real-estate mogul Donald Trump has repeatedly mocked presidential rival Ben Carson since it was revealed that Carson believes an unusual theory about the Egyptian pyramids.

"I think it's a ridiculous situation. I mean he's talking about the pyramids were made for grain," Trump said of Carson during a Fox Business interview on Friday. "And if you look at the pyramids, they're solid."

On Wednesday, BuzzFeed published a 1998 video where Carson argued that the Bible supports the idea that the pyramids were built to store grain. He said he still held that view after the story was published.

Historians believe that the pyramids were generally built as tombs for Ancient Egypt's pharaoh rulers, not to house grain.

During his Friday interview on Fox Business, Trump combined Carson's unusual beliefs about the pyramids with the controversy over Carson's claims of being a violent teenager.

Carson said he once attacked his mother with a hammer and tried to stab a friend before having an epiphany and becoming the soft-spoken person he is today.

A CNN investigation into Carson's past could not corroborate any of his reported violent incidents. But they happened as far back as 50 years ago, and Carson said he is protecting the victims' identities from the media.

Trump slammed Carson and similarly labeled that controversy "ridiculous."

"He's trying to justify it. They can't find the people. I said this is the first time in the history of the world where a politician is running on the basis that he tried to stab [somebody] and some people are saying he's not credible, OK? The whole thing is ridiculous," Trump said.

Trump repeatedly jabbed at Carson on Twitter as well: