The Bible Says:
Therefore go and make disciples of all nations, baptizing them in the name of the Father, and of the Son and of the Holy Spirit, and teaching them to obey everything I have commanded you. And surely I am with you always, to the very end of the age
Matthew 28:19-20
"Everyone who calls on the name of the Lord will be saved."
How, then can they call on the one that they have not believed in? And how can they believe in the one of whom they have not heard? And how can they hear withoug someone preaching to them? And how can they preach unless they are sent?
Romans 10:13-15