People intuitively know that stealing is wrong. Maybe stealing is wrong because it violates the social institution of property which is reasonably and appropriately instituted by each community. Maybe stealing is a violation of the natural relation that an agent has to an object upon mixing her labor with it. Maybe stealing violates a divine command. But people's intuitive knowledge that stealing is wrong does not come from their knowledge of such reasons for the wrongness of stealing. So how is it knowledge?
It's not like when the child knows Pythagoras' Theorem to be true but can't prove it. For she knows the theorem to be true because she gets her belief from the testimony of other people who can prove it. But that's not how the knowledge that stealing is wrong works. People can intuitively know that stealing is wrong without their belief having come directly or indirectly from some brilliant philosopher who came up with a good argument for its wrongness.
Perhaps there is some evolutionary story. Communities where there was a widespread belief that stealing is wrong survived and reproduced while those without the belief perished, and there was no knowledge at all the back of the belief formation. However, perhaps, it came to be knowledge, because this evolutionary process was sensitive to moral truth. However, it is dubious that this evolutionary process was sensitive to moral truth as such. It was sensitive to the non-moral needs of the community, and sometimes this led to moral truth and sometimes to moral falsehood (as, for instance, when it led to the conviction that it is right to enslave members of other communities). So if this is the story where the belief came from, it's not a story about knowledge. At best, the intuitive conviction that stealing is wrong, on this story, is a justified true belief, but it's Gettiered.
This, I think, is an interesting puzzle. There is, presumably, a very good reason why stealing is wrong, but the intuitions that we have do not seem to have the right connection to that reason.
Unless, of course, we did ultimately get the knowledge from someone who has a very good argument for the wrongness of stealing. As I noted, it is very implausible that we got it from a human being who had such an argument. But maybe we got it from a Creator who did.