Euripides, Heracles
E. P. Coleridge, Ed.

Iris
Courage, old men! she, whom you see, is Madness, daughter of Night, and I am Iris, the handmaid of the gods. We have not come to do your city any hurt, [825] but our warfare is against the house of one man only, against him whom they call the son of Zeus and Alcmena. For until he had finished all his grievous labors, Destiny was preserving him, nor would father Zeus ever suffer me or Hera to harm him. [830] But now that he has accomplished the labors of Eurystheus, Hera wishes to brand him with the guilt of shedding kindred blood by slaying his own children, and I wish it also. Come then, unwed maid, child of black Night, harden your heart relentlessly, [835] send forth frenzy upon this man, confound his mind even to the slaying of his children, drive him, goad him wildly on his mad career, shake out the sails of death, that when he has conveyed over Acheron's ferry that fair group of children by his own murderous hand, [840] he may learn to know how fiercely against him the wrath of Hera burns and may also experience mine; otherwise, if he should escape punishment, the gods will become as nothing, while man's power will grow.

Madness
Of noble parents was I born, the daughter of Night, sprung from the blood of Ouranos; [845] and these prerogatives I hold, not to use them in anger against friends, nor do I have any joy in visiting the homes of men; and I wish to counsel Hera, before I see her err, and you too, if you will hearken to my words. This man, against whose house you are sending me, has made himself a name alike in heaven [850] and earth; for, after taming pathless wilds and raging sea, he by his single might raised up again the honors of the gods when sinking before man's impiety; . . . wherefore I counsel you, do not wish him dire mishaps.