I wrote to that young leader that powerful preaching consists of
Then, a preacher has to watch God work. He does things that only He can do. He says,
For as the rain and the snow come down from heaven and do not return there but water the earth, making it bring forth and sprout, giving seed to the sower and bread to the eater, so shall my word be that goes out from my mouth; it shall not return to me empty, but it shall accomplish that which I purpose, and shall succeed in the thing for which I sent it.
Isaiah 55:11-12 (ESV)