Letter 1108: Virtue must be practiced with all one's strength — not merely admired from a distance.

To Arsenouphios. On the Apostle, that "This man is a chosen vessel for me." "This man is a chosen vessel for me" [Acts 9:15]: Christ says this concerning Paul, when he entrusts to him the apostolic preaching. For he would not, in handing over the Church for which he poured out his precious blood, have delivered her to a teacher who was not going to contribute a virtue that matched the grace; nor would he have given this testimony, had he seen that Paul's eagerness did not correspond to the magnitude of the matter. For he wished the preaching to run everywhere, its goodness being made known not only by word but also by way of life. For the signs, even one might receive them in a wicked condition; but an upright life stops the mouth even of the devil himself. Therefore let not those who are unwilling to take any forethought for an upright life suppose that the preaching prevailed by the signs alone. For the life of those who preached also worked together with the deeds done and the words spoken, giving no handle [for accusation]. If, then, even now the life of our instructors were to vie with the apostolic manner of life, perhaps signs too would come to pass. But if they did not come to pass, [an upright life] would suffice for the enlightenment of those who behold it.

Περὶ τοῦ Ἀποστόλου, ὅτι «Σκεῦος ἐκλογῆς μοί ἐστιν οὗτος». «Σκεῦος ἐκλογῆς μοί ἐστιν οὗτος», περὶ Παύλου φησὶν ὁ Χριστὸς, ὅτε τὸ ἀποστολικὸν αὐτῷ ἐκήρυγμα ἐγχειρίζεσιν. Οὐ γὰρ ἂν, ὑπὲρ ἧς τὸ τίμιον αἷμα ἐξέχεεν Ἐκκλησίας, ταύτην φέρων παραδέδωκε διδασκάλῳ μὴ μέλλοντι τὴν ἀρετὴν ἀντίρροπον συνοίσειν τῇ χάριτι· ἀλλ' οὐδὲ ταύτην ἐποιεῖτο τὴν μαρτυρίαν, μὴ συμβαίνουσαν ὁρῶν αὐτοῦ τὴν προθυμίαν τῷ μεγέθει τοῦ πράγματος. Τρέχειν γὰρ τὸ κήρυγμα πανταχοῦ ἐβούλετο, οὐ μόνον τῷ λόγῳ, ἀλλὰ καὶ τῷ τρόπῳ τὴν χρηστότητα γνωρούμενον. Τὰ μὲν γὰρ σημεῖα καὶ ὁποίαν δύναται δέξασθαι πονηρὰν (57)· βίος δὲ ὀρθὸς, καὶ αὐτοῦ τοῦ διαβόλου ἐμφράττει τὸ στόμα. Μὴ τοίνυν ἐκ τῶν σημείων μόνον νομιζέτωσαν (58) κεκρατηκέναι τὸ κήρυγμα, οἱ μηδεμίαν βίου ὀρθοῦ βουλόμενοι ποιείσθαι πρόνοιαν. Συνέπραττε γὰρ τοῖς γινομένοις καὶ λεγομένοις καὶ τὸ κηρυττόντων βίος, μηδεμίαν λαβὴν διδούς. Εἰ τοίνυν καὶ νῦν ὁ τῶν ὑφηγητῶν βίος ἤμιλλᾶτο τῇ ἀποστολικῇ πολιτείᾳ, ἴσως μὲν καὶ σημεῖα ἐγίνετο. Εἰ δὲ μὴ ἐγίνετο, ἤρκει πρὸς φωτισμὸν τῶν ὁρώντων.