Those whom the gods wish to destroy they first make mad.

Anonymous ancient proverb, wrongly attributed to Euripides. The version here is quoted as a "heathen proverb" in Daniel, a Model for Young Men (1854) by William Anderson Scott. The origin of the misattribution to Euripides is unknown. Several variants are quoted in ancient texts, as follows.

For cunningly of old was the celebrated saying revealed: evil sometimes seems good to a man whose mind a god leads to destruction. | Sophocles, Antigone 620-3, a play pre-dating any of Euripides' surviving plays. An ancient commentary explains the passage as a paraphrase of the following, from another, earlier poet. | When a god plans harm against a man, he first damages the mind of the man he is plotting against. | Quoted in the scholia vetera to Sophocles' Antigone 620ff., without attribution. The meter (iambic trimeter) suggests that the source of the quotation is a tragic play. | For whenever the anger of divine spirits harms someone, it first does this: it steals away his mind and good sense, and turns his thought to foolishness, so that he should know nothing of his mistakes. | Attributed to "some of the old poets" by Lycurgus of Athens in his Oratio In Leocratem [Oration Against Leocrates], section 92. Again, the meter suggests that the source is a tragic play. These lines are misattributed to the much earlier semi-mythical statesman Lycurgus of Sparta in a footnote of recent editions of Bartlett's Familiar Quotations and other works. | The gods do nothing until they have blinded the minds of the wicked. | Whom Fortune wishes to destroy she first makes mad. | Publilius Syrus, Maxim 911 | The devil when he purports any evil against man, first perverts his mind. | As quoted by Athenagoras of Athens in Legatio Pro Christianis. | quem Iuppiter vult perdere, dementat prius. | "Whom Jupiter wishes to destroy, he first sends mad"; neo-Latin version. Similar wording is found in James Duport's Homeri Gnomologia (1660), p. 234. "A maxim of obscure origin which may have been invented in Cambridge about 1640" -- Taylor, The Proverb (1931). Probably a variant of the line "He whom the gods love dies young", derived from Menander's play The Double Deceiver via Plautus (Bacchides 816-7). | quem (or quos) Deus perdere vult, dementat prius. | Whom God wishes to

and derived paraphrases || in Dictionary of Quotations (Classical) (1906), compiled by Thomas Benfield Harbottle, p. 433.