8 For I tell you that Christ became a servant to the circumcised to show God's truthfulness, in order to confirm the promises given to the patriarchs, 9 and in order that the Gentiles might glorify God for his mercy. As it is written,
“Therefore I will praise you among the Gentiles,
and sing to your name.”
10 And again it is said,
“Rejoice, O Gentiles, with his people.”
11 And again,
“Praise the Lord, all you Gentiles,
and let all the peoples extol him.”
12 And again Isaiah says,
“The root of Jesse will come,
even he who arises to rule the Gentiles;
in him will the Gentiles hope.”
13 May the God of hope fill you with all joy and peace in believing, so that by the power of the Holy Spirit you may abound in hope. (Romans 15:8-13 (ESV)
There is only one God and he is the God of hope for both the Jews and the Gentiles. He fulfilled his promise to the Jews through Jesus Christ, the root of Jesse that came, that the Gentiles might glorify God for his mercy. Now he rules the Gentiles.
This isn’t an earthly rule, because on the one hand this was already true of God before Jesus came. God is God of God and King of Kings, he raised up Babylon and he caused Babylon to fall. The Egyptians did not need to recognize his rule as they worshiped the false gods of the Nile, but God still ruled over them as even Pharaoh’s magicians seemed to realize when the recognized the finger of God at work in the plagues that Moses sent. God still rules over all the nations of the earth as Paul explains in Romans 13, and this despite all the craziness of the current election cycle.
But this is more true because Christ came not to establish and earthly kingdom. “My kingdom is not of this world” he says. The world rules, and God rules in the world through coercion and law, by rewarding the good and punishing the wicked. And when the wicked is Caesar the punishment comes with a senate full of daggers.
The kingdom that Christ came to establish is a heavenly kingdom that changes hearts through the forgiveness of sins, that rules through love and faith that causes us to trust in him. This is the kingdom we pray for when we pray “thy kingdom come on earth as it is in heaven,” this kingdom is the rule of faith that inspires the Christian to hallow God’s name in thought, word and deed, to live by his word. It is a kingdom established by love that washes over us in a flood of grace streaming from the cross in his blood. There he reigns from his throne, dying that we might live and serve him in his kingdom even now serving him in everlasting innocence, blessedness and righteousness. His is an awesome rule of hope that overcomes all things because he has overcome the world with all its tribulations, he rose from the dead.