Isocrates 1.19 (tr. George Norlin):
If you love knowledge, you will be a master of knowledge. What you have come to know, preserve by exercise; what you have not learned, seek to add to your knowledge; for it is as reprehensible to hear a profitable saying and not grasp it as to be offered a good gift by one's friends and not accept it. Spend your leisure time in cultivating an ear attentive to discourse, for in this way you will find that you learn with ease what others have found out with difficulty. Believe that many precepts are better than much wealth; for wealth quickly fails us, but precepts abide through all time; for wisdom alone of all possessions is imperishable. Do not hesitate to travel a long road to those who profess to offer some useful instruction; for it were a shame, when merchants cross vast seas in order to increase their store of wealth, that the young should not endure even journeys by land to improve their understanding.
ἐὰν ᾖς φιλομαθής, ἔσει πολυμαθής. ἃ μὲν ἐπίστασαι, ταῦτα διαφύλαττε ταῖς μελέταις, ἃ δὲ μὴ μεμάθηκας, προσλάμβανε ταῖς ἐπιστήμαις· ὁμοίως γὰρ αἰσχρὸν ἀκούσαντα χρήσιμον λόγον μὴ μαθεῖν καὶ διδόμενόν τι ἀγαθὸν παρὰ τῶν φίλων μὴ λαβεῖν. κατανάλισκε τὴν ἐν τῷ βίῳ σχολὴν εἰς τὴν τῶν λόγων φιληκοΐαν· οὕτω γὰρ τὰ τοῖς ἄλλοις χαλεπῶς εὑρημένα συμβήσεταί σοι ῥᾳδίως μανθάνειν. ἡγοῦ τῶν ἀκουσμάτων πολλὰ πολλῶν εἶναι χρημάτων κρείττω· τὰ μὲν γὰρ ταχέως ἀπολείπει, τὰ δὲ πάντα τὸν χρόνον παραμένει· σοφία γὰρ μόνον τῶν κτημάτων ἀθάνατον. μὴ κατόκνει μακρὰν ὁδὸν πορεύεσθαι πρὸς τοὺς διδάσκειν τι χρήσιμον ἐπαγγελλομένους· αἰσχρὸν γὰρ τοὺς μὲν ἐμπόρους τηλικαῦτα πελάγη διαπερᾶν ἕνεκα τοῦ πλείω ποιῆσαι τὴν ὑπάρχουσαν οὐσίαν, τοὺς δὲ νεωτέρους μηδὲ τὰς κατὰ γῆν πορείας ὑπομένειν ἐπὶ τῷ βελτίω καταστῆσαι τὴν αὑτῶν διάνοιαν.