Republican presidential candidate Ben Carson on Thursday said he stands by comments made in 1998, in which he claimed Joseph built the pyramids in Egypt to store grain. And for three days, it has become a 2106 issue.

In a video posted by BuzzFeed of a commencement speech at Andrews University, a school associated with the Seventh-day Adventist Church, Carson said, “My own personal theory is that Joseph built the pyramids to store grain. Now all the archeologists think that they were made for the pharaohs’ graves. But, you know, it would have to be something awfully big if you stop and think about it. And I don’t think it’d just disappear over the course of time to store that much grain.

“And when you look at the way that the pyramids are made, with many chambers that are hermetically sealed, they’d have to be that way for various reasons,” added Carson.

Experts who were asked about the issue dismissed Carson’s claim. According to Tel Aviv University’s Dr. Deborah Sweeney, “We can clearly see, from looking at the long sequence of these buildings, that pyramids were built as tombs for the king.”

But Carson refused to back off that claim during an interview with CBS News on Wednesday. “It’s still my belief, yes,” he said. “The pyramids were made in a way that they had hermetically sealed compartments….You would need that if you were trying to preserve grain for a long period of time.”

Republican presidential frontrunner mocked his rival for first place over the claim. “I think I’ll have to put that into my repertoire when I talk about Ben,” he said on MSNBC’s “Morning Joe” program Thursday. “That was a strange … that was a strange deal.”

“I think it’s a ridiculous situation. I mean he’s talking about the pyramids were made for grain,” Trump reitreated during a Firday morning interview on Fox Business. “And if you look at the pyramids, they’re solid.”