Holy Spirit power...

I fear that if you take the preaching throughout the Church of Christ and ask why there is, alas! so little converting power in the preaching of the Word, why there is so much work and often so little result for eternity, why the Word has so little power to build up believers in holiness and in consecration,—the answer will come: It is the absence of the power of the Holy Ghost. And why is this? There can be no other reason but that the flesh and human energy have taken the place that the Holy Ghost ought to have. 

-Andrew Murray