Most impromptu speeches are not worth the paper they are written on

The very best impromptu speeches are the ones written well in advance.

A verbal contract isn't worth the paper it's written on.

Some say that the memoranda of understanding aren't worth the paper they are written on,

You are not worth another word, else I'd call you knave.

He hath not fed of the dainties that are bred in a book; he hath not eat paper, as it were; he hath not drunk ink.