τῆς Περσίδος γλώσσης ὅσα ἠδύνατο κατενόησε

From LSJ

ἄνευ γὰρ φίλων οὐδεὶς ἕλοιτ᾽ ἂν ζῆν, ἔχων τὰ λοιπὰ ἀγαθὰ πάντα → without friends no one would choose to live, though he had all other goods

Source

English > Greek (Woodhouse Quotes Reversed)

he learnt all that he could of the Persian tongue