“My own personal theory is that Joseph built the pyramids to store grain. Now all the archaeologists 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 a reason. And various scientists have said, “Well, you know there were alien beings that came down and they have special knowledge and that’s how they were”—you know, it doesn’t require an alien being when God is with you.”

Stated in 1998 during his commencement address at Andrews University, as quoted in "Aliens, Pyramids, and Granaries? What on Earth Was Ben Carson Thinking?" http://www.theatlantic.com/notes/2015/11/aliens-pyramids-and-granaries-what-on-earth-was-ben-carson-thinking/414301/, The Atlantic, (November 4, 2015)