1) The Promise (Gen 12:1-3) – Because God has promised to bless all nations (or people groups) on the earth. What better motivation and encouragement can we have than the understanding that missions (blessing the nations with the Gospel) is in the sure purposes of God.
2) The Purchase (Rev 5:9) – Because Jesus has already purchased people from every tribe and nation with His blood. Like the Moravians motivated by this purchase we should repeat what two Moravians missionaries said as they set sail for India, “May the Lamb receive the reward of His suffering!” In other words, He has already purchased them, our job is only to gather in what is His.
3) Because the Harvest is plentiful (Matt 9:37) – Now this is for all the numbers gurus out there who are motivated by sheer statistics. Today, out of the 6.5 billion people on the planet, over 4 billion are without a saving relationship with Christ. More tragic is that 2.4 billion of these who are lost have no means to hear the message of salvation through Christ – they are cut off from the gospel through lack of missionaries, lack of resources, etc. If you lined them up in a single file line they would wrap around the earth 25 times...The harvest is plentiful!
4) Because the Laborers are few (Matt 9:37) – This is probably what runs through my head the majority of the times I get up to speak. Only one in every 20,000 believers will ever take the gospel to those who are out of reach of the church. What’s worse than that? Out of all the cross-cultural missionaries in the world, you would hope that the majority would be working where the majority need is. However only 2.5% of all the 430,000 missionaries are working in the 10/40 Window. More laborers are needed.
5) Because the Destiny of the Lost (Rom 1; John 3:18; John 14:6) – Now this is harder to take in, but I believer the Bible gives us no means by which a person can be saved other than through Christ’s work, and by exercising faith in His name. This means not by other religions, not without hearing specifically about Christ (through evangelism and missions) and not because they died without hearing. The Scripture leaves no loopholes for those living in ignorance. All are born in sin, the Cross has real meaning for salvation, and the Great Commission is necessary for people to hear and be saved. If this shocks you, you may have been influenced by the universalism that is gossiped among church goers. In Romans 1 (creation) does exactly what God designed it to do – it condemns people, leaving them without an excuse and knowledge of a creator – but not salvific knowledge of God through Jesus Christ. This makes missions not only important, but urgent.
6) Logically Necessary for Hearing the Gospel Message (Rom 10:14-15, Acts 8 (Philip) and 10 (Cornelius)) – This goes along with the last one. Every time someone comes to Christ in Scripture there is a human messenger involved. It would be great to think that God would draw people to Himself in the world apart from someone going. He is able, but this is not the means He has chosen to use. The Church is the means. The Ethiopian eunuch was reading Isaiah (the OT Bible!) and still God miraculously transported Philip, a human messenger to explain Christ to him. An angel appears to Cornelius, a god-fearer. But still Peter must be summoned and travel all the way to Cornelius’ house to explain the gospel to him before he could be saved. Why didn’t the angel just tell Cornelius? It would have saved a lot of time and gas money for Peter – but God used a human messenger. Missions and evangelism are necessary.
7) The Example of the Church (Acts 1:8, 10, 15, Rom 15:20) – The early church has given us a model to follow. They went out, sent out their own missionaries like Paul and Barnabus, and evangelized the Gentiles beyond the reach of the gospel in their world.
8) The Descriptive Future is Prescriptive for Today (Rev 7:9, Rev 21:24-26) – Now, it’s tricky but follow this logic. If there are people described in heaven in the future – it is logical that they must be reached with the gospel at some point in history. So because we see a great multitude gathered around the throne from every tribe, people, and nation – we must labor to begin with this end in mind, bringing it into reality as God uses us to fulfill it.
9) Because We Will be Held Accountable (Ezek 33) – Here is a passage that will cause you to re-evaluate life. The people of God, meant to be a blessing to the world, were held accountable for not warning others of the danger coming. Will believers be held accountable for their obedience to the Great Commission? It may mean great reward-loss by many Christians for failing to use what God has blessed them with to bless the nations.
10) Because To Whom Much is Given Much is Required (Luke 12:47-48) – Here is Jesus’ measuring standard. It’s like a blessing and obedience math formula. Our accountability may be based on our resources, our understanding, or our ability – more given equals more expected.
11) Because the Church is the Means (Rom 1:5, Gal 3:14-15, 2 Cor 5:17-20) – You are God’s ordained means for the blessing of Christ reaching to all the nations, just like He promised (Gen 12). Jesus has purchased them (Rev 5:9) and commissioned us with the task of gathering them in for God’s glory.
12) Because History Awaits the Fulfillment of the Promise (Matt 24:14) – Not sure how it’s all going to play out, but if God has promised that all nations are reached and Jesus says here that the gospel will be preached to all nations…then the end will come – it just seems logical. The story of history seems to be arranged on the thread of this mission, even the history we are a part of today. That is exciting!
13) Because the Glory of God is Yet to be Known (Hab 2:14; Ps 72:19, 86; Isa 11:9) – There are actually about a dozen times that Bible talks of God’s glory “filling the earth as the waters cover the sea.” God has created people to worship Him and that worship is being given to other lesser things right now. Missions is spreading the worship and enjoyment of God to those who are not currently worshippers, because God’s glory is increased by the increase of His church in the world. As John Piper says it, “Missions exists because worship doesn’t. Where passion for God is weak, zeal for missions will be weak.”
14) The Commands of Jesus (Matt 28:18-20; Acts 1:8, 13:47; John 20:21) – And last of all – because Jesus commanded it. Just as Jesus says in John 14:21, "He who has My commandments and keeps them is the one who loves Me,” or 1 John 3:24, “The one who keeps His commandments abides in Him.” I hope we can all stand before him in the end and hear him say, “Well done, good and faithful servant.”