Buddha Always focused on voidness?

I remember reading about the characteristics of the or a Buddha, and one of them was “a Buddha is always focused on voidness.” Sadly I did not save the website and don’t remember where this was written. Now to the question. What are the mental characteristics of a Buddha? Can you give me a list? I don’t mean the nine qualities. It is a different list, a less common one. It should include the point I mentioned and be of mahayana origin.