“Know that against time the gods themselves are powerless.”

Die Jungfrau von Orleans (The Maid of Orleans) (1801), Act III, sc. vi (as translated by Anna Swanwick)
Variants of the most commonly quoted portion:
Against stupidity the gods themselves contend in vain.
Against stupidity the gods themselves labor in vain.
Against stupidity the gods themselves fight unvictorious
Against stupidity even the gods contend in vain.
Against stupidity gods themselves contend in vain.
With stupidity the gods themselves contend in vain.
With stupidity the gods themselves struggle in vain.
Context: Folly, thou conquerest, and I must yield!
Against stupidity the very gods
Themselves contend in vain. Exalted reason,
Resplendent daughter of the head divine,
Wise foundress of the system of the world,
Guide of the stars, who art thou then if thou,
Bound to the tail of folly's uncurbed steed,
Must, vainly shrieking with the drunken crowd,
Eyes open, plunge down headlong in the abyss.
Accursed, who striveth after noble ends,
And with deliberate wisdom forms his plans!
To the fool-king belongs the world.

Source: Dictionary of Burning Words of Brilliant Writers (1895), P. 329.

VALIS (1981)

Source: Comfort and Protest (1987), p. 71

Source: Fear of Flying

All the Pretty Horses (1992)

1960's, Conversations with Samuel Beckett and Bram van Velde' (1965 - 1969)

Between Man and Man (1965), p. 15
Between Man and Man (1965)

Source: Cibola Burn (2014), Chapter 34 (p. 345)