Plato, Laws 728b

τούτοις πᾶσιν πᾶς ἄνθρωπος ψυχὴν θειότατον ὂν ἀτιμότατα καὶ κακοσχημονέστατα διατιθείς. τὴν γὰρ λεγομένην δίκην τῆς κακουργίας τὴν μεγίστην οὐδεὶς ὡς ἔπος εἰπεῖν λογίζεται, ἔστιν δʼ ἡ μεγίστη τὸ ὁμοιοῦσθαι τοῖς οὖσιν κακοῖς ἀνδράσιν, ὁμοιούμενον δὲ τοὺς μὲν ἀγαθοὺς φεύγειν ἄνδρας καὶ λόγους καὶ ἀποσχίζεσθαι, τοῖς δὲ προσκολλᾶσθαι διώκοντα κατὰ τὰς συνουσίας· προσπεφυκότα δὲ τοῖς τοιούτοις ἀνάγκη ποιεῖν

everyone who acts thus is treating most dishonorably and most disgracefully that most divine of things, his soul. Hardly anyone takes account of the greatest judgment (as men call it) upon evil-doing; that greatest judgment is this,—to grow like unto men that are wicked, and, in so growing, to shun good men and good counsels and cut oneself off from them, but to cleave to the company of the wicked and follow after them; and he that is joined to such men inevitably acts and is acted upon in the way that such men bid one another to act.