Lucian, Life of Demonax 37

καὶ μάντιν δέ ποτε ἰδὼν δημοσίᾳ ἐπὶ μισθῷ μαντευόμενον, “οὐχ ὁρῶ,” ἔφη, “ἐφ’ ὅτῳ τὸν μισθὸν ἀπαιτεῖς· εἰ μὲν γὰρ ὡς ἀλλάξαι τι δυνάμενος τῶν ἐπικεκλωσμένων, ὀλίγον αἰτεῖς ὁπόσον ἂν αἰτῇς, εἰ δὲ ὡς δέδοκται τῷ θεῷ πάντα ἔσται, τί σου δύναται ἡ μαντική;”

And once, when he saw a fortune-teller telling fortunes for a fee, he said, ‘I don’t see the reason why you ask for a fee: if you are able to change any of the things that have been fated, then whatever you charge will be too small an amount, but if everything will happen in the way the god has decided, what does your fortune-telling achieve?’