We are not saved only to be instruments for God, but to be His sons and daughters. He does not turn us into spiritual agents but into spiritual messengers, and the message must be a part of us. The Son of God was His own message— “The words that I speak to you are spirit, and they are life” (John 6:63). As His disciples, our lives must be a holy example of the reality of our message. Even the natural heart of the unsaved will serve if called upon to do so, but it takes a heart broken by conviction of sin, baptized by the Holy Spirit, and crushed into submission to God’s purpose to make a person’s life a holy example of God’s message.
There is a difference between giving a testimony and preaching. A preacher is someone who has received the call of God and is determined to use all his energy to proclaim God’s truth. God takes us beyond our own aspirations and ideas for our lives, and molds and shapes us for His purpose, just as He worked in the disciples’ lives after Pentecost. The purpose of Pentecost was not to teach the disciples something, but to make them the incarnation of what they preached so that they would literally become God’s message in the flesh. “…you shall be witnesses to Me…” (Acts 1:8).
Allow God to have complete liberty in your life when you speak. Before God’s message can liberate other people, His liberation must first be real in you. Gather your material carefully, and then allow God to “set your words on fire” for His glory.