THIS verse spoken by David is a prophecy concerning Jesus Christ. We know this because Jesus uses it in Matthew 22:44 to show the Pharisees that David was inspired to speak these words of him. Peter interprets this verse in his sermon on the day of Pentecost as refering to Jesus. In a similar way we have the same meaning given to this verse in Hebrews 1:13 and Hebrews 10:13.
David prophecies concerning Christ that he is the Son of God and David's Lord. From the New Testament references mentioned above, we know that David was prophesying concerning Christ's ascension into heaven to sit at God's right hand on the throne of heaven, and reign together with God the Father. So Jesus who lived and died and rose again, when he ascended to heaven, ascended to take up a positon besides God in reigning over the world all down history.
Let us take to heart and believe what David's prophecy tells us. It tells us that Jesus is the Son of God, one with God the Father in all things, God of gods and King of kings.
Let us take to heart and believe that Jesus is reigning over the world and all history, and he reigns until all his enemies, all who oppose him and God, are defeated and placed under his sentence and authority. All the world is under Christ's dominion and will in the end be brought to submission before him. This means that all who do not own Jesus as Lord and God, and believe on him as their God and Saviour, will in the end be brought to submit to him and God the Father, and receive from him the just due and sentence that their rebellion deserves.
From this prophecy of David we learn that only those who believe on Jesus and submit to him as Lord and God will be saved from everlasting destruction in hell. Let us believe and submit to him while we are able.