Epictetus, Works, book 3, Ὅτι ἀπὸ πάντων τῶν ἐκτὸσ ἔστιν ὠφελεῖσθαι. 10:

οὔ· ἀλλ’ ὁ μὲν τοῦ τραχήλου καθάπτων καὶ τὴν ὀσφῦν μου καὶ τοὺσ ὤμουσ καταρτίζων ὠφελεῖ με καὶ ὁ ἀλείπτησ καλῶσ ποιῶν λέγει "ἆρον ὕπερον ἀμφοτέραισ" καὶ ὅσῳ βαρύτερόσ ἐστιν ἐκεῖνοσ, τοσούτῳ μᾶλλον ὠφελοῦμαι ἐγώ· εἰ δέ τισ πρὸσ ἀοργησίαν με γυμνάζει, οὐκ ὠφελεῖ με;