Go into all the world!

The Bible tells us that the gospel must, and will, be spread amongst every possible people group on the earth - and that we who believe in Jesus Christ are to be the ones who get off our backsides and go and do it:

And Jesus came and spoke to them, saying, "All power is given unto me in heaven and in earth. Go therefore, and disciple all nations, baptizing them in the name of the Father, and of the Son, and of the Holy Spirit, teaching them to observe all things whatsoever I have commanded you: and, behold, I am with you always, even to the end of the world." (Matthew 28:18-21)

After this I looked, and, behold, a great multitude, which no man could number, of all nations, and kindreds, and people, and tongues, stood before the throne, and before the Lamb, clothed with white robes, and palms in their hands; and cried with a loud voice, saying, "Salvation to our God who sits upon the throne, and to the Lamb." (Revelation 7:9-10)

According to the reports I've seen on the news today (in relation to the photographing of an as-yet uncontacted tribe, e.g. here), there are believed to be around 100 tribes in the world who have not had any contact at all made with them.

That's 100 tribes that Christian's have to make efforts to reach. No doubt many will be murdered when they try. Nevertheless, Revelation 7:9-10 assures us that the effort ultimately will be a success. There's no greater privilege in the world than being the first to preach the gospel to people who've never heard it before.