Epictetus, Works, book 4, Περὶ ἐλευθερίασ. 126:

ἀλλ’ ὅτι λέγομεν ἥμερον εἶναι τοῦ ἀνθρώπου τὴν φύσιν καὶ φιλάλληλον καὶ πιστήν, τοῦτο παράδοξον οὐκ ἔστιν; ‐ Οὐδὲ τοῦτο.