[ding_dong_daddy_from_dumas]

As the late Yogi Berra might say, "Those verbal instructions ain't worth the paper they're written on!"

[Verginius Rufus]

Along the lines of something Samuel Goldwyn might have said (”a verbal contract isn’t worth the paper it’s written on”—according to Wikipedia a misquotation of what Samuel Goldwyn actually said).

[Liz]

A double-pinky promise?

I guess that clinches it (smirk).