Old Lutheran Quote (I'm stealing this from Weedon)

"The preacher's planting and watering and the hearer's running and hearing would both be in vain and no conversion would follow it if the power and effectiveness of the Holy Spirit were not added (I Cor. 3:6-7). The Spirit enlightens and converts hearts through the Word preached and heard. So people believe this Word and agree with it. Neither preacher nor hearer is to doubt this grace and effectiveness of the Holy Spirit. They should be certain that when God's Word is preached purely and truly, according to God's command and will, and people listen attentively and seriously and meditate on it, God is certainly present with His grace. He grants, as has been said, what otherwise a person can neither accept nor give by his own powers. For we should not and cannot always judge from feeling about the presence, work, and gifts of the Holy Spirit, as to how and when they are experienced in the heart. They are often covered and happen in great weakness. Therefore, we should be certain about and agress with the promise that God's Word preached and heard is truly an office and work of the Holy Spirit. He is certainly effective and works in our hearts by them (II Cor. 2:14-17; 3:5-6)."

Formula of Concord, Solid Declaration II