Plato, Laws 717c

γεννησάντων καὶ θρεψαμένων πρὸς τὸ παρέχειν αὐτὰ εἰς ὑπηρεσίαν ἐκείνοις κατὰ δύναμιν πᾶσαν, ἀρχόμενον ἀπὸ τῆς οὐσίας, δεύτερα τὰ τοῦ σώματος, τρίτα τὰ τῆς ψυχῆς, ἀποτίνοντα δανείσματα ἐπιμελείας τε καὶ ὑπερπονούντων ὠδῖνας παλαιὰς ἐπὶ νέοις δανεισθείσας, ἀποδιδόντα δὲ παλαιοῖς ἐν τῷ γήρᾳ σφόδρα κεχρημένοις. παρὰ δὲ πάντα τὸν βίον ἔχειν τε καὶ ἐσχηκέναι χρὴ πρὸς αὑτοῦ γονέας εὐφημίαν

so that he ought to give them service to the utmost of his power—with substance, with body, and with soul, all three—thus making returns for the loans of care and pain spent on the children by those who suffered on their behalf in bygone years, and recompensing the old in their old age, when they need help most. And throughout all his life he must diligently observe reverence of speech towards his parents above all things,