I recall reading somewhere that there are different sources of moral rules, I think things being sacred was one of them, 'purity' might have been another one or the same one, and if anyone remembers the three things I would appreciate knowing.

You probably have in mind the theories of Jonathan Haidt.

I am skeptical towards his theories, though. There may be some truth in them, but his approach is extremely ideologized and, in my opinion, biased accordingly. (On the other hand, I do appreciate that he is explicit and upfront about his ideology and its role in his work. It is certainly a welcome contrast to what is commonly seen in academia.)