The power of preaching is found in the Spirit working with the Word of God and through the Word of God. God promises that His Word will not return to Him void. Its power is located not in the eloquence or erudition of the preacher but in the power of the Spirit. Preaching is a tool in the hands of the Spirit of God. The Holy Spirit is a supernatural being, the third person of the Trinity. His presence in preaching is what makes it a supernatural event.
Salvation is a divine achievement. No man can save himself. God sovereignly ordains not only the end (salvation) but the means to the end (preaching). We conclude then that what is going on Sunday morning when the Word of God is truly preached is a divine drama of redemption.