1 Corinthians 4:19-20:

But I will come to you shortly, if the Lord will, and will know, not the speech of them which are puffed up, but the power.
For the kingdom of God is not in word, but in power.

Notes on 1 Corinthians 4:19-20:

Paul looked down on powerless preaching.  It is abnormal in God’s eyes.  Real gospel preaching is done in the power of the Holy Spirit.  We should expect God to confirm His Word when it is preached boldly, if for no other reason than that He said that He would!

This is the difference between Christianity and other religions.  Christianity is not a philosophy that we have to convince people to believe.  People treat it as such until they see resurrection power in demonstration.  Then they have to stop and think.

If we are powerless like the puffed-up preachers Paul mentioned, we need to check what we are preaching and make sure that it is God’s Word.  God cannot confirm human junk such as “God makes you a better Christian through suffering sickness.”  No one who preaches that stuff should expect any power to follow, because there’s no Word in it for God to confirm.  “God doesn’t do those things anymore” becomes a self-fulfilling prophecy, at least for the current audience.  We also need to see if we are being bold like the apostles.  If we tiptoe through the tulips on healing because we know that preaching that healing is for all makes some people mad, we are not doing the kind of bold preaching that got results for the apostles.

See also:

Objection: Paul Told Timothy to Drink Wine Instead of Believing God for Healing