Preaching wisdom from an ancient church father
Timeless wisdom from St. Ambrose of Milan (4th Century)...
The one who reads much and understands what is read is filled, and, once filled, is a source of life-giving water to others. For, as the Scripture says, "If the clouds be filled they shall pour rain down upon the earth." Let your sermons, therefore, stream forth, pure and lucid; gently fill the minds of your people with good doctrine, and with pleasing words soften their hearts so that you may lead them on the right way.
Let your discourse be filled with wisdom. Then it will need no confirmation from others; of itselt if will be effective. Let no word you speak be frivilous or merely for effect.