Arrian, Discourses of Epictetus
3.21.4-6 (tr. Thomas Wentworth Higginson):
The carpenter does not come and say, Hear me talk about the carpenter's art; but having undertaken to build a house, he makes it, and proves that he knows the art. You also ought to do something of the kind; eat like a man, drink like a man, dress, marry, beget children, do the office of a citizen, endure abuse, bear with an unreasonable brother, bear with your father, bear with your son, neighbour, companion. Show us these things that we may see that you have in truth learned something from the philosophers.
οὐκ ἔρχεται ὁ τέκτων καὶ λέγει "ἀκούσατέ μου διαλεγομένου περὶ τῶν τεκτονικῶν," ἀλλ᾿ ἐκμισθωσάμενος οἰκίαν ταύτην κατασκευάσας δείκνυσιν, ὅτι ἔχει τὴν τέχνην. τοιοῦτόν τι καὶ σὺ ποίησον· φάγε ὡς ἄνθρωπος, πίε ὡς ἄνθρωπος, κοσμήθητι, γάμησον, παιδοποίησον, πολίτευσαι· ἀνάσχου λοιδορίας, ἔνεγκε ἀδελφὸν ἀγνώμονα, ἔνεγκε πατέρα, ἔνεγκε υἱόν, γείτονα, σύνοδον. ταῦτα ἡμῖν δεῖξον, ἵν᾿ ἴδωμεν, ὅτι μεμάθηκας ταῖς ἀληθείαις τι τῶν φιλοσόφων.