Our Scripture reading today is Romans 10:13-15.
Verse 14, "How then shall they call on him in whom they have not believed? and how shall they believe in him of whom they have not heard? and how shall they hear without a preacher?"
The mode that God chose to spread the message of salvation is through the preaching of the Gospel of Jesus Christ.  He could have delivered the message Himself our used any or all of His angels.  Instead, God has given us the responsibility and privilege to deliver the life changing message of the Gospel.  
All of God's children have been called to be preachers of the Gospel.  The Apostle Paul writes in 1 Corinthians 9:16, "For though I preach the gospel, I have nothing to glory of: for necessity is laid upon me; yea, woe is unto me, if I preach not the gospel!"  It is not an option to consider, but a command to be obeyed.  We are commissioned to deliver the TRUTH in love.  Ephesians 4:15, "But speaking the truth in love..."  If you have received and believed the Gospel message, you are qualified to share it with others.  As we are filled with the Spirit of God, we will have boldness and compassion preach the Gospel through our walk and talk.