An old, widely used phrase expressing the sentiment that revenge that is delayed, and executed well after the
heat of anger has dissipated, is more satisfying than revenge taken as an immediate act of rage.
It has been frequently been claimed on the Internet to have originated in the novel "Les Liaisons Dangereuses" by Pierre Choderlos de Laclos. In
truth, however, there are
two problems with the widely circulated quotation from that
book. The first is that the phrase does not appear in the novel, or anything else that de Lacois wrote. The second problem is that the French quotation used as
proof is linguistically erroneous; de Lacois would
never have written the words attributed to him. Thus it bears all the hallmarks of an Internet "fact" for which someone invented an authentication that seemed plausible, knowing that it would rarely be verified.
The phrase has been in use since at least the 19th century, and at least one author's use of it back then expressed to the reader that it was an already existing dictum.
Of course, how
long ago it came into being in the Klingon Empire would be an
interesting subject for xenolinguistic research.
"
Kirk, old friend, do you know the Klingon proverb, 'Revenge is a
dish best served
cold'?"
– Khan Noonien Singh in "Star Trek II: The Wrath of Khan"