Hand in the face?

[Nu1]

I believe it is a violation for a defender to place his/her hand directly in front of an offensive player's face - to block their vision (I think it is a player without the ball?)...but I cannot locate this in my Rule or Case book.

I thought I read this in one of those, but cannot find it now. Brain freeze, I guess. Or maybe I'm making the whole thing up Can anyone help?