1 Thessalonians 1:5
…because our gospel came to you not only in word, but also in power...

When the gospel comes, it must first arrive in word. This is to remove any doubt about what is being taught or expressed. The name of Christ is to be boldly proclaimed. What other message is worth giving? What other message has any eternal value in sharing? Those who wear the name of Christ, who are Christians, must be quick to speak His name, His word, and His message of reconciliation.

As the gospel is taught and shared, there are signs that accompany it and authenticate it. These signs are described by Paul and should be used as a standard by which we can judge our teaching: If we fail to share the gospel in word, then we have failed to share the gospel. 

Likewise, the gospel must come in power. This is not a power of human manufacturing or design, but rather a power that is created and fueled by the authority of Jesus Christ. Did our Lord not begin the great commission with the declaration that "All authority in heaven and on earth has been given to me." [Matthew 28:18]? We don't go in our own power, for we are merely sinners saved by grace. Instead, we go in the power of Jesus Christ, the One who has "overcome the world" [John 16:33].

Do not be lulled into thinking that sharing the gospel in power means it will always be received and accepted in the way we hope. Paul certainly knew what it meant to be rejected and persecuted, yet he did not abandon the work of Christ. He knew, as we can know, that God's power is stronger than the world and sufficient for our needs. It is why Paul later wrote to Timothy, "for God gave us a spirit not of fear but of power and love and self-control." [2 Timothy 1:7]

The gospel must come in word, and it must come in the power of the Spirit of God. It is He alone who can convict and redeem. "For by grace you have been saved through faith. And this is not your own doing; it is the gift of God, not a result of works so that no one may boast." [Ephesians 2:8-9]