The quotation is from Dante's Inferno, Canto III, and is the last part of the inscription over the gate of Hell. the full inscription is:

Per me si va nella città dolente;
per me si va nell'eterno dolore;
per me si va tra la perduta gente.

Giustizia mosse il mio alto Fattore;
fecemi la divina Potestate.
la somma Sapienza e il primo Amore.

Dinanzi a me non fur cose create,
se non eterne, ed io eterno duro;
lasciate ogni speranza, voi ch'entrate.

Through me the road to the city of desolation,
through me the road to sorrows diuturnal,
through me the road among the lost creation.

Justice moved my great Maker; God eternal
wrought me: the Power, and the unsearchably
high Wisdom, and the primal love supernal.

Nothing ere I was made was made to be
save things eterne, and I eterne abide;
lay down all hope, you that go in by me.

transl. by Dorothy L. Sayers