Plato, Laws 769c

τις ἐπινοήσειε γράψαι τε ὡς κάλλιστον ζῷον καὶ τοῦτʼ αὖ μηδέποτε ἐπὶ φαυλότερον ἀλλʼ ἐπὶ τὸ βέλτιον ἴσχειν τοῦ ἐπιόντος ἀεὶ χρόνου, συννοεῖς ὅτι θνητὸς ὤν, εἰ μή τινα καταλείψει διάδοχον τοῦ ἐπανορθοῦν τε, ἐάν τι σφάλληται τὸ ζῷον ὑπὸ χρόνων, καὶ τὸ παραλειφθὲν ὑπὸ τῆς ἀσθενείας τῆς ἑαυτοῦ πρὸς τὴν τέχνην οἷός τε εἰς τὸ πρόσθεν ἔσται φαιδρύνων ποιεῖν ἐπιδιδόναι, σμικρόν τινα χρόνον αὐτῷ πόνος παραμενεῖ πάμπολυς; ἀληθῆ.

Suppose that a man should propose to paint an object of extreme beauty, and that this should never grow worse, but always better, as time went on, do you not see that, since the painter is mortal, unless he leaves a successor who is able to repair the picture if it suffers through time, and also in the future to improve it by touching up any deficiency left by his own imperfect craftsmanship, his interminable toil will have results of but short duration? True.