Taken from: http://communio.stblogs.org/index.php/2010/12/saint-ambrose-2/
Drink, then, from Christ, so that your voice may also be heard. Store up in your mind the water that is Christ, the water that praises the Lord. Store up water from many sources, the water that rains down from the clouds of prophecy.
Whoever gathers water from the mountains and leads it to himself or draws it from springs, is himself a source of dew like the clouds. Fill your soul, then, with this water, so that your land may not be dry, but watered by your own springs.
He who reads much and understands much, receives his fill. He who is full, refreshes others. So Scripture says: If the clouds are full, they will pour rain upon the earth.
Therefore, let your words be rivers, clean and limpid, so that in your exhortations you may charm the ears of your people. And by the grace of your words win them over to follow your leadership. Let your sermons be full of understanding. Solomon says: The weapons of the understanding are the lips of the wise; and in another place he says: Let your lips be bound with wisdom. That is, let the meaning of your words shine forth, let understanding blaze out.