CHORUS: But fairy tales that scare us humans
are useful for religion.

[ΧΟΡΟΣ: φοβεροὶ δὲ βροτοῖσι μῦ-
θοι κέρδος πρὸς θεῶν θεραπεί-
αν.]

Euripides (485?-406? BC) Greek tragic dramatist

Electra [Ἠλέκτρα], l. 743ff, Antistrophe 2 (c. 420 BC) [tr. Wilson (2016)]
    (Source)

Following recounting of a story in which Zeus made the sun move backwards in the sky to punish Thyestes for his treachery.

(Source (Greek)). Alternate translations:

Fresh strength is added to religion's base
By fables which man's breast with terror fill.
[tr. Wodhull (1809)]

But tales that frighten men are profitable for service to the gods.
[tr. Coleridge (1891)]

But stories terrible to mortals are a gain for the worship of the gods.
[tr. Buckley (1892)]

Yet it may be the tale liveth, soul-affraying,
To bow us to Godward in lowly obeying.
[tr. Way (1896)]

Once, men told the tale, and trembled;
Fearing God.
[tr. Murray (1905)]

Such shocking myths are for the good of men, to frighten them into believing in the gods.
[tr. Theodoridis (2006)]

But tales which terrify mankind
are profitable and serve the gods.
[tr. Johnston (2009)]