Plato, Laws 721b

γαμεῖν δέ, ἐπειδὰν ἐτῶν ᾖ τις τριάκοντα, μέχρι ἐτῶν πέντε καὶ τριάκοντα, εἰ δὲ μή, ζημιοῦσθαι χρήμασίν τε καὶ ἀτιμίᾳ, χρήμασι μὲν τόσοις καὶ τόσοις, τῇ καὶ τῇ δὲ ἀτιμίᾳ.ὁ μὲν ἁπλοῦς ἔστω τις τοιοῦτος περὶ γάμων, ὁ δὲ διπλοῦς ὅδε—γαμεῖν δέ, ἐπειδὰν ἐτῶν ᾖ τις τριάκοντα, μέχρι τῶν πέντε καὶ τριάκοντα, διανοηθέντα ὡς ἔστιν ᾗ τὸ ἀνθρώπινον γένος φύσει τινὶ μετείληφεν ἀθανασίας, οὗ καὶ πέφυκεν ἐπιθυμίαν

and under five and thirty; if he fails to do so, he shall be punished both by a fine in money and by degradation, the fine being of such and such an amount, and the degradation of such and such a kind. Such shall be the simple form of marriage law. The double form shall be this,—A man shall marry when he is thirty years old and under thirty-five, bearing in mind that this is the way by which the human race, by nature’s ordinance, shares in immortality, a thing for which nature has implanted in everyone a keen desire.