Scripture never explicitly tells us where Adam and Eve’s son, Cain, got his wife, but let’s think about it.

We know Adam and Eve were the first people, so Cain’s wife had to come from them. And Genesis tells us they had “other sons and daughters.” So Cain must’ve married his sister or maybe his niece.

But isn’t this incest? Well, God didn’t forbid close relations marrying until the time of Moses, hundreds of years later. And it wasn’t a problem originally because the human genome was created perfect. It wasn’t until after sin that mistakes started piling up in our DNA making it dangerous for close relations to have kids.