Plato, Laws 916d

νόμον, τῆς τιμῆς τε ἀποδότω τῷ πριαμένῳ τριπλάσιον.ὁ δὲ ἀλλαττόμενος ἢ νόμισμα ἀντὶ νομίσματος, ἢ καὶ τῶν ἄλλων ζῴων ὁτιοῦν ἢ καὶ μὴ ζῴων, ἀκίβδηλον πᾶν διδότω καὶ δεχέσθω τῷ νόμῳ συνεπόμενος· προοίμιον δέ, καθάπερ ἄλλων νόμων, δεξώμεθα καὶ περὶ ὅλης ταύτης τῆς κάκης. κιβδηλείαν δὲ χρὴ πάντα ἄνδρα διανοηθῆναι καὶ ψεῦδος καὶ ἀπάτην ὡς ἕν τι γένος ὄν, τοῦτο ᾧ τὴν φήμην ἐπιφέρειν εἰώθασιν οἱ πολλοί, κακῶς λέγοντες, ὡς ἐν καιρῷ

He that exchanges for money either money or anything else, living or not living, shall give and receive every such article unadulterated, conforming to the law; and touching all knavery of this sort, as in the case of other laws, let us hearken to a prelude. Adulteration should be regarded by every man as coming under the same head as falsehood and fraud—a class of actions concerning which the mob are wont to say, wrongly, that any such action will generally be right if it be done opportunely: