What does it mean that believers are the extension of Heaven on earth?
Believers are ambassadors for Christ, citizens of Heaven living in foreign territory. As Heaven's extension on earth, they represent their home government, carrying out the designs, hopes, and aspirations of their homeland, which is Christ. They are to tell a lost world reconciliation is accomplished and stand as a dam in a river of iniquity until He lifts them out.
Les explains that because our citizenship is in Heaven, we live as citizens of Heaven in a foreign land. An ambassador is a representative of a home government in a foreign country, so believers are Christ's ambassadors and the extension of Heaven here on earth. Our responsibility is to carry out the designs, hopes, and aspirations of our homeland, which is Christ, and to let the lost world know that God was in Christ reconciling the world unto Himself, not imputing their trespasses, and has committed unto us the word of reconciliation. If we don't do it, who will? Paul makes clear in Thessalonians that the true Church, the believer, is like a dam in a river of iniquity; one day He will lift us out, and that river will flood the planet like never before, but until then we are to be that dam and stand in the gap.