It must be preached in every nation, and we are also commanded to preach it to every person. This responsibility is not for just a few. It is given to the whole church of Jesus Christ. We are the light of the world. We are the salt of this earth.
Salt is a preserving substance.
The only thing that is keeping this world from the judgments of God is the presence of His church on this earth. We cannot reach this world when we are not even willing to reach our neighbour. A certain man went down from Jerusalem to Jericho, and fell among thieves, which stripped him of his raiment, and wounded him, and departed, leaving him half dead. And likewise a Levite, when he was at the place, came and looked on him, and passed by on the other side. And went to him, and bound up his wounds, pouring in oil and wine, and set him on his own beast, and brought him to an inn, and took care of him.