In Psalms, chapter two, verse eight, no earthly king was ever given this promise of the nations as an inheritance. It was a promise made only to the Son of God, Christ Jesus. God the Father promises a harvest of souls from the nations to God the Son as His rightful inheritance, and it will come to pass, as in Revelation seven, verses nine through ten, chapter eleven, verse fifteen, chapter twenty-one, verses twenty-three to twenty-four, and chapter twenty-two, verse two.
Psalms two, verse eight, is under the triumph of the king section, which stems from verses one through twelve. The heathen are the ungodly who are the people that oppose God. No earthly king has ever given this promise because they are from the earth, not from heaven. God made man in His image, as in Genesis one, verse twenty-six. “And God said, Let us make man in our image, after our likeness: and let them have dominion over the fish of the sea, and over the fowl of the air, and over the cattle, and over all the earth, and over every creeping thing that creepeth upon the earth.”
Through this privilege, the ungodly have overstepped their boundaries, believing they can access and control everything, as in verses two through three. However, that is not the case because God is the only one who made the heaven and the earth, oversees all things, and sets the boundaries of what can and cannot be done, as in verses four to five. The inheritance of the heathen can only come through Jesus Christ, the Son of God, who is the One who redeemed the human race to have access to God by salvation. No other being has done this but the Almighty God Himself. In the end, it will come to pass.