Revelation 20:7-8

7When the 1,000 years have finished, God will let Satan go free out of his prison.

8Satan will then go and deceive people in nations everywhere in the world. He will make them believe him. Those nations are God's enemies, Gog and Magog. Satan will bring them together to fight a war against God's people. Satan's army has many people, as much as the sand on the shore of the sea.