Romans 10:12-17 For there is no distinction between Jew and Greek; the same Lord is Lord of all, bestowing his riches on all who call on him. 13 For “everyone who calls on the name of the Lord will be saved.” 14 But how are they to call on him in whom they have not believed? And how are they to believe in him of whom they have never heard? And how are they to hear without someone preaching? 15 And how are they to preach unless they are sent? As it is written, “How beautiful are the feet of those who preach the good news!” 16 But they have not all obeyed the gospel. For Isaiah says, “Lord, who has believed what he has heard from us?” 17 So faith comes from hearing, and hearing through the word of Christ.
Clearly this text tells us that we are called to preach the gospel to the nations. We can say both that God is sovereign over evangelism and that people will not be saved if we do not preach. This is because God has ordained his children as the means by which his gospel will be preached. I preach the gospel because God has worked a deep love and passion for Jesus in my heart and I cannot help but to tell people about the hope that is me (1 Peter 3:15). Evangelism is an issue of obedience-we are all commanded as believers to make disciples of all nations (Matthew 28:18-20). Further, as I mentioned earlier, Acts 18:10 indicates that when we go preach the gospel there is always the sure hope that “there are many” in the places we preach who are God’s people. In other words, if we know that God has chosen those who would believe before the foundations of the world, then we can be sure that our preaching is not in vain-God will use it. God’s Word is powerful and His gospel is the power of God unto salvation (Romans 1:16). God’s Word will not return void, it will always accomplish what the Lord sets it out to accomplish (Isa. 55:11). If we love God, we will long to see His name honored and glorified among the nations and we will long to be obedient to him by making disciples of all nations. Evangelism is obedience issue-those who love the Lord and long to be with Him will speak His name to the nations!
Thus it is completely foreign to Reformed Theology (or Biblical Theology for that matter) not to evangelize, because the man who is reformed realizes that God has been gracious to him beyond what he deserves and he realizes that if he has truly been saved that he will long to tell others of the “excellencies of Christ” (1 Peter 2:9). Thus if you have someone who says that they are saved but has no desire to tell others of Christ, it might be that they are not really a Christian. Because those who are born in Christ will not live in a continual pattern of sin (1 John 3:9) and if someone refuses to evangelize-they are living in unrepentant sin as they are directly disobeying a clear mandate in Scripture (Matt. 28:18-20) and may not be a Christian.
So far from inhibiting evangelism, faith in the sovereignty of God’s government and grace is the only thing that can sustain it, for it is the only thing that can give us the resilience that we need if we are to evangelize boldly and persistently, and not be daunted by temporary setbacks. So far from being weakened by this faith [faith in the absolute sovereignty of God], therefore, evangelism will inevitably be weak and lack staying power without it (J. I. Packer, Evangelism and the Sovereignty of God, 10).