He who cheats with an oath acknowledges that he is afraid of his enemy, but that he also thinks little of God.

[ὁ γὰρ ὅρκῳ παρακρουόμενος τὸν μὲν ἐχθρὸν ὁμολογεῖ δεδιέναι, τοῦ δὲ θεοῦ καταφρονεῖν.]

Plutarch (AD 46–127) Greek historian, biographer, essayist [Mestrius Plutarchos]

Parallel Lives, “Lysander” [tr. Leman (1688)]
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(Source (Greek))

Criticizing the Spartan leader's use of oathbreaking to gain advantage over his enemies.

See Montaigne (1578).