What's the equivalent idiomatic English expression for "verba volant, scripta manent"?
Solution 1:
This concept is often expressed in English by the phrase:
A verbal agreement isn't worth the paper it's written on.
It is attributed to Samuel Goldwyn, the Polish American film producer and wit, after he had promised a role to an actress.
Another version is
An oral contract isn't worth the paper it's written on.
This is sometimes called Goldwyn's Law.