Plutarch, Platonicae quaestiones, chapter 1, section 2 2:

ἂν εἶναι τῶν Ὀλυμπίων ἀγωνοθέτας, εἰ μηδὲ εἷς Ἠλείων ἦν ἀγωνιστής, οὕτως ὁ μέλλων ἐν λόγοις ὀρθῶς ἐπιστατήσειν καὶ βραβεύσειν οὐ δίκαιός·??