Read when I was a kid, 40ish years ago. Probably written longer ago than that-1950s-60s? Seems like an Asimov story, but I looked at a list with synopses of all his short stories and didn’t recognize it. No luck googling.
So the plot is: technology has been developed to create “wormholes” (though I doubt they were called that) to create shortcuts through great distances in space. One use is for easy commuting over long distances. So the main character takes a daily short walk through his own personal tunnel-like wormhole to his job many miles away. One day he notices a “tear” in the wall of his wormhole, and goes through it out of curiousity. It goes to a desert where he sees a group of tiny people with primitive clothing living there. It turns out they’re Moses and the Israelites, and the tear in his wormhole created a path through time as well as space. The reason they’re so small is because the universe has expanded since the time of Moses, and according to the story the expansion affected the entire fabric of the universe. Of course the man gets a literal God complex and starts ordering the little Israelites around, and becomes the God of the Old Testament. Sound familiar?
Bonus question: as a kid I was fascinated by the idea that an expanding universe meant that everything was expanding, not just the space between galaxies. I’m pretty positive now that’s not the case though. The universe expanding means just the space between galaxies, right?
It rings a small bell - there certainly are stories in which time travel and changes in size go together (the best known is “Time Locker” by Lewis Padgett, but that’s clearly not your story. I’ll think about it.
On the bonus question, yeah, it’s the space between galaxies (or even the space between clusters of galaxies) - as said in “Annie Hall” - “Brooklyn is not expanding”
That’s because the gravitational attraction within and between close galaxies keeps them together.
It definitely is not an Asimov story. Not at all like him.
OP, was this story in an anthology or in a magazine?