What does Psalm 47:8 mean?

This psalm has praised God for His absolute authority over all the earth. Some commentators see this as a general praise. Others find prophetic parallels to the eventual rule of the Messiah, Jesus Christ. Still others suggest it refers to an actual instance of God's mighty power rescuing Israel from her enemies. The phrase "the nations" is often used in the Bible to mean the entire world outside of Israel (Leviticus 26:33; 1 Samuel 8:5; Psalm 2:1; 79:6; Isaiah 52:10). The God of Israel is not merely concerned with a single people, but is the Creator and Lord of the whole earth. Praise for God's power might come in reference to His demonstrated power over those who attacked Israel.

It's possible Psalm 47 was written in response to the miraculous defeat of enemy forces during the reign of Jehoshaphat. Multiple enemy nations joined to attack Israel, but were defeated without God's chosen people needing to fight at all (2 Chronicles 20). Language and phrases used in that account closely resemble those used is this psalm.

Another incident involved Sennacherib, an Assyrian king. He bragged that God Himself could not stop the conquest of Jerusalem (2 Kings 19:10–13). However, King Hezekiah of Judah believed the true God was able to deliver the city. He prayed, "O LORD, the God of Israel, enthroned above the cherubim, you are the God, you alone, of all the kingdoms of the earth; you have made heaven and earth" (2 Kings 19:15). He asked God to save the people of Jerusalem from the enemy (2 Kings 19:19). God answered Hezekiah's prayer, demonstrating the truth of this verse: that He reigns over the nations and sits on His holy throne. The King of Assyria was mighty, but he and his thousands of soldiers were unable to withstand the judgment of the God who is almighty. The Lord struck a fatal blow to the Assyrian soldiers and ended their siege of the city (2 Kings 19:35–37).