Plato, Laws 721a

πρώτην πόλεων πέρι κατακοσμήσει ταῖς τάξεσιν; τί μήν; ἀρχὴ δʼ ἐστὶ τῶν γενέσεων πάσαις πόλεσιν ἆρʼ οὐχ ἡ τῶν γάμων σύμμειξις καὶ κοινωνία; πῶς γὰρ οὔ; γαμικοὶ δὴ νόμοι πρῶτοι κινδυνεύουσιν τιθέμενοι καλῶς ἂν τίθεσθαι πρὸς ὀρθότητα πάσῃ πόλει. παντάπασι μὲν οὖν. λέγωμεν δὴ πρῶτον τὸν ἁπλοῦν, ἔχοι δʼ ἄν πως ἴσως ὧδε—

first the starting-point of generation in States? Of course. Does not the starting-point of generation in all States lie in the union and partnership of marriage?. Certainly. So it seems that, if the marriage laws were the first to be enacted, that would be the right course in every State. Most assuredly. Let us state the law in its simple form first: how will it run? Probably like this:—A man shall marry when he is thirty years old