Is it the wording you seek, or the idea? You will find an exegesis on the idea in Progress and Poverty, pp. 408-21 and 433-39. George, of course, was not the first to get the idea, either, although few have expressed it with such vigor and conviction. Turgot, the Physiocrats, and later Walras made much of it; Hotelling cites Jules Dupuit, too. I wouldn't doubt that a busy scholar might find it in Cicero, Epictetus, Virgil, or Aristotle. It's too obvious a matter for intelligent people to miss. Mason Gaffney