Preserving Health

Ὅτι σύ κύριε κατὰ μόνας ἐν ἐλπίδι κατῴκισάς με Τί δέ ἐστι, Κατὰ μόνας; Τῶν πονηρῶν χωρίς. Τὴν γὰρ εἰρήνην ταύτην κατώρθωσα, φησὶ, πρὸς σὲ, καὶ κατὰ μόνας οἰκῶ φεύγων τοὺς διεφθαρμένους. Καὶ μάλα εἰκότως. Καθάπερ γὰρ σώματα πολλάκις ἀπὸ τῆς τῶν ἀέρων τῶν διεφθαρμένων λύμης ἀπολλυνται· οὕτω δὴ καὶ ψυχὴ πολλάκις ἐδέξατο βλάβην ἀπὸ τῆς τῶν πονηρῶν συνουσίας· καὶ καθὰπερ ὀφθαλμὸς ὑγιαίνων, ὅταν νοσοῦντα ἴδῃ, πλήττεται, καὶ ὁ ψώρας ἐμπεπλησμένος, μεταδίδωσι καὶ τοῖς ὑγιαίνουσιν· οὕτω δὴ συμβαίνει πολλάκις καὶ ἐπὶ τῆς συνουσίας τῶν πονηρῶν ἀνθρώπων. Διὰ τοῦτο καὶ ὁ Χριστὸς παρῇνει οὐ μόνον φευγειν τοὺς τοιούτους, ἀλλὰ καὶ ἐκτέμνειν, οὕτω λέγων· Εἰ δὲ ὁ ὀφθαλμός σου ὁ δεξιὸς σκανδαλίζει σε, ἔξελε αὐτὸν, καὶ βάλε ἀπὸ σοῦ· οὐ δὴ περὶ ὀφθαλμοῦ λέγων· τί γὰρ ἄν ἀδικήσειεν ὀφθαλμὸς, διανοίας ὑγιαινούσης; ἀλλὰ περὶ φίλων ἀναγκαίων καὶ ἐν τάξει τῶν μελῶν τούτων ἡμῖν ὄντῶν, καὶ βλαπτόντων ἡμᾶς, ταῦτα ἐνομοθέτησε, κελεύων καὶ τὴν φιλίαν τῶν τοιούτων ἀτιμάζειν, ὥστε τὴν σωτηρίαν τὴν ἑαυτῶν ἀσφαλεστέραν  ποιεῖν. Ἅγιος Ἰωάννης ὁ Χρυσόστομος, Εἰς Τον Δ' Ψαλμον

For you, Lord, alone in hope have established me. 1 What is this 'alone'? It is without the wicked. For this is the peace, it says, established for you, that you dwell alone, fleeing them who corrupt. And most rightly. For as bodies are often ruined by corrupt air, so even the soul is often harmed by the company of the wicked. And as the eye of the healthy when it gazes on the sick is struck, and he who is diseased is overwhelmed, so it is with those who are healthy, who are so often infected by association with the wicked. And therefore Christ exhorts not only flight from such folk, but even that they be cut off, for He says, 'If your right eye scandalises you, pluck it out, and cast it from you.' 2 He is not speaking of the eye itself; for what evil did it do if the soul is healthy? But this is about the influence of associates who are to us as parts of the body, and if they harm us, this He commands, calling us to be rid of such friendships, so attending to the preservation of salvation. Saint John Chrysostom, from the Exposition of the Psalms, Psalm 4 1 Ps 4.10 2 Mt 5.29