Plato, Laws 917b

ὁ κιβδηλεύων τι ψεύδεται καὶ ἀπατᾷ καὶ τοὺς θεοὺς παρακαλῶν ἐπόμνυσιν ἐν τοῖς τῶν ἀγορανόμων νόμοισίν τε καὶ φυλακτηρίοις, οὔτε ἀνθρώπους αἰδούμενος οὔτε θεοὺς σεβόμενος. πάντως μὲν δὴ καλὸν ἐπιτήδευμα θεῶν ὀνόματα μὴ χραίνειν ῥᾳδίως, ἔχοντα ὡς ἔχουσιν ἡμῶν ἑκάστοτε τὰ πολλὰ οἱ πλεῖστοι καθαρότητός τε καὶ ἁγνείας τὰ περὶ τοὺς θεούς· εἰ δʼ οὖν μὴ πείθοιτο, ὅδε νόμος· ὁ πωλῶν ὁτιοῦν ἐν ἀγορᾷ μηδέποτε δύο εἴπῃ τιμὰς ὧν ἂν πωλῇ,

who adulterates any market commodity, lies and deceives and, calling Heaven to witness, takes an oath in front of the laws and cautions of the market-stewards, neither regarding men nor revering gods. Certainly it is a good practice to refrain from sullying lightly divine names, and to behave with such purity and holiness as most of us generally exhibit in matters of religion; if however this rule is disobeyed, the law runs thus:—He that sells any article in the market shall never name two prices for what he is selling;