Apophthegmata Laconica

Plutarch

Plutarch. Moralia, Vol. III. Babbitt, Frank Cole, translator. Cambridge, MA: Harvard University Press; London: William Heinemann Ltd., 1931 (printing).

Polydorus, the son of Alcamenes, when a certain man was continually making threats against his enemies, said, Don’t you see that you are using up the best part of your vengeance?