Gentlemen: You have undertaken to cheat me. I won't sue you, for law is too slow. I'll ruin you.

Said to be the entirety of a letter to Charles Morgan and C. K. Garrison, quoted in an obituary, "Commodore Vanderbilt's Life" (5 January 1877) New York Times. Stiles in The First Tycoon doubted the existence of such a letter although, as seen above, Vanderbilt was inclined to act on his own rather than sue.