7.9.2-3 (tr. William Melmoth):
In the first place, then, I look upon it as a very advantageous practice (and it is what many recommend) to translate either from Greek into Latin or from Latin into Greek. By this means you acquire propriety and dignity of expression, and a variety of beautiful figures, and an ease and strength of exposition, and in the imitation of the best models a facility of creating such models for yourself. Besides, those things which you may possibly have overlooked in an ordinary reading over cannot escape you in translating: and this method will also enlarge your knowledge, and improve your judgment.
utile in primis, et multi praecipiunt, vel ex Graeco in Latinum vel ex Latino vertere in Graecum. quo genere exercitationis proprietas splendorque verborum, copia figurarum, vis explicandi, praeterea imitatione optimorum similia inveniendi facultas paratur; simul quae legentem fefellissent, transferentem fugere non possunt. intellegentia ex hoc et iudicium acquiritur.