Today With Zwingli: On the Importance of Preaching, and Preachers

As a proclaimer of the Word, the Pastor must not stop preaching simply because of opposition or because there is no visible success connected to his efforts. He is to be a living example of the love of God, and a living example is more important than 100,000 words.

And in another place-

The work of preaching I believe to be most holy, so that above any other duty it is in the highest degree necessary. For in speaking canonically or regularly we see that among all nations the outward preaching of apostles and evangelists or bishops has preceded faith, which we nevertheless say is received by the Spirit alone. For alas! We see very many who hear the outward preaching of the gospel, but believe not, because a dearth of the Spirit has occurred.