Boy - talk about topic drift!
The legal principles of fair use and copyright are certainly important ones, but wholly irrelevant to the OP's question wrt a quote from Milton, who has been dead for approx 350 years and all of whose works can be quoted, misquoted, used, abused, and freely handled by any writer in any way without any legal or moral barrier. Unless you're referencing a specific edition of his works there's no need for a formal attribution, never mind mention on the copyright page. (In fact, noting Milton on the copyright page would look silly, not respectful.)