So now, Cyclops, you know how it should look in beautiful modern Greek. Ordinarily, we recommend that, in the case of a quotation like this that was originally composed and well put in a modern language, you stay with a modern language rather than forcing it pointlessly into a dead language. But if you really need to know how the phrase (as you wrote it) would have looked in ancient Greek, it would be something like
κρεῖττόν που συγγνώμην ὕστερον ζητοῦν ἢ ἐξουσίαν πρότερον αἰτεῖν.