WILDE: I wish I had said that.
WHISTLER: You will, Oscar, you will.

Oscar Wilde (1854-1900) Irish poet, wit, dramatist
(Attributed)

An anecdotal exchange between Wilde and James Whistler, associated with how Wilde was known for reusing epigrams and witticisms from various folk, usually not crediting them.

References to the exchange date back, in various sources and forms, as far as 1886, with the specific language varying, and the original bon mot from (usually) Whistler not mentioned. More details and discussion: “I Wish I Had Said That” “You Will, Oscar, You Will” – Quote Investigator®.