All hope abandon, ye who enter here.
(Dante: Lasciate ogne speranza, voi ch'intrate.)
The source for the proverb is Forty Thousand Quotations: Prose and Poetical by Charles Noel Douglas (Bartleby.com). The poster is made with AutoMotivator. The illustration is by Gustave Doré for Dante's Inferno, Canto III, at Wikipedia.