Plato, Laws 643b

λέγοντος τοίνυν ἐμοῦ τί ποτε χρὴ φάναι παιδείαν εἶναι, σκέψασθε ἂν ἀρέσκῃ τὸ λεχθέν. λέγοις ἄν. λέγω δή, καί φημι τὸν ὁτιοῦν ἀγαθὸν ἄνδρα μέλλοντα ἔσεσθαι τοῦτο αὐτὸ ἐκ παίδων εὐθὺς μελετᾶν δεῖν, παίζοντά τε καὶ σπουδάζοντα ἐν τοῖς τοῦ πράγματος ἑκάστοις προσήκουσιν. οἷον τὸν μέλλοντα ἀγαθὸν ἔσεσθαι γεωργὸν ἤ τινα οἰκοδόμον, τὸν μὲν οἰκοδομοῦντά τι τῶν παιδείων

Then while I am stating how education ought to be defined, you must be considering whether you are satisfied with my statement. Proceed with your statement. I will. What I assert is that every man who is going to be good at any pursuit must practice that special pursuit from infancy, by using all the implements of his pursuit both in his play and in his work. For example, the man who is to make a good builder