Some people might think they’re being called by God as a missionary, so how can they know for sure?
On Mission Now
If you believe that God might be calling you as a missionary, let me ask you a question. Have you been on mission for Christ where you live, where you work, and wherever you go today? If you have not been boldly sharing the gospel yet, you are probably not ready to be a missionary. God will not use a person as a missionary if they’ve been silent about the gospel in their life. Jeremiah the Prophet couldn’t keep quiet. Neither could the Apostle Paul, or the Apostle Peter, or the other biblical characters. Jeremiah  described the passion to proclaim God’s Word like this: “If I say, ‘I will not mention him, or speak any more in his name,’ there is in my heart as it were a burning fire shut up in my bones, and I am weary with holding it in, and I cannot” (Jer 20:9). Does that describe you? Peter and the disciples were told to stop spreading the news about Jesus, but they replied, “we cannot but speak of what we have seen and heard” (Acts 4:20). Is that you? Can you not help but speak of Christ? Can you not contain it within your heart and feel compelled to tell others? The word “woe” in the Bible is a word of judgment, so Paul goes so far as to say, “For necessity is laid upon me. Woe to me if I do not preach the gospel” (1st Cor 9:16b)! Has God laid that “necessity” to be His witness on your heart? Paul said he had no choice but to preach, he could not help but to proclaim Christ, and like Jeremiah, it was like a fire that was impossible to contain and could not hold it in? Is that you? If you are not on mission now where you live, or find it difficult to speak of Christ, or your heart does not break for those who are perishing, you might not be called as a missionary…at least not yet.
All on Mission
I don’t believe what one man told me a few years ago. He said, “Evangelizing is the pastor’s job. We’re not called to do that,” to which I replied, “We’re all called as ministers of the gospel, and to all Jesus commands us to “go,” into all the world,” but especially next door. If we’ve not been faithful in sowing God’s Word now, He will not see any reason to use you in a greater capacity in the future, like being a missionary. Jesus said, “One who is faithful in a very little is also faithful in much, and one who is dishonest in a very little is also dishonest in much” (Luke 16:10), so if we’re not on mission for Christ today, even a little bit, then we are not going to be faithful in the big things, which is what a missionary trip is. I see no reason why God would use us for much if we aren’t even being faithful in little. God is looking for men and women who can boldly proclaim the gospel unashamedly. To be a foreign missionary takes a lot of training, knowing about the culture, the language, the customs, and things that most of us don’t think about. It’s never a quick decision. It must be basked in prayer and studying God’s Word. It is only when you step out for Christ on a local basis that He might consider using you (or me) for the bigger things, besides, the fields are so ripe here in the states but we don’t have enough witnessing here in this country, so it’s a shame to think of going somewhere else to evangelize when we’re not even doing it with our family or at work or any place else you go.
Greatest Need for Missionaries
I thought that most of the greatest needs for missionaries was overseas or in Brazil somewhere, but one Southern Baptist missionary told me years ago that the U.S. is the ripest field for missionaries to work, so to him, it’s sad that we send missionaries all over the world but neglect the greater harvest that is here in the States, lying ripe in the fields. For some reason, most Americans think they’re good people, but the Bible says otherwise. I asked several people if they thought they were going to heaven and why, and nearly every one of them said, “I’ve done a lot of good things for people and I think God will see that and let me into heaven,” but speaking of works, God says they’re nothing more than dirty rags (Isaiah 64:6) and to be honest, “None is righteous, no, not one” (Rom 3:1), and “no one understands; no one seeks for God” (Rom 3:11), and in fact, “All have turned aside; together they have become worthless; no one does good, not even one” (Rom 3:12). I think the reason Paul says “not one” is righteous is because there is always that one person who declares their own goodness, so that includes all of us. It’s only because of Jesus’ righteousness that we can stand before God (2nd Cor 5:21). We are saved for works but not by works, so works alone is worthless to save, so with so many self-proclaimed “good people” in the U.S., we need missionaries here to tell them, “No, none of us will ever be good enough to go to heaven….it takes Jesus’ righteousness, not filthy rags.” People get offended when I tell them that every one of us falls infinitely short of God’s glory (Rom 3:23 ) and holy standard, so I keep mentioning God’s requirement for righteousness, not their own. It is the most extreme vetting there is.
I believe that a person who is being called to be a missionary will have such an overwhelming call that they cannot help but be on mission, and with this calling, there is a deep and abiding passion for the lost people of a certain nation. It’s not a decision to take lightly. I think you’ll know whether you’re being called as a missionary or not, and the best evidence of that is having the same desire to save those who are perishing where you live now. If you or I are being silent about Christ right now and we have no history of witnessing to others, then it’s probably not your calling, but if you’re like Paul or Jeremiah who cannot help but speak, and care little about what it costs in personal time and finances and rejection, then you might be called. Talk to your pastor, church leaders or perhaps even another missionary before you go, but by all means, “Go” into all the world…today, in your own little section of the world and be faithful in witnessing for Christ now. Otherwise, you might think twice about becoming a missionary.
Read more on this subject: How to Become a Christian Missionary 
Resource – Scripture quotations are from The Holy Bible, English Standard Version® (ESV®), Crossway Bibles. (2007). ESV: Study Bible : English standard version. Wheaton, Ill: Crossway Bibles. Used by permission. All rights reserved.