I will tell of the decree: The Lord said to me, "You are my Son; today I have begotten you. Ask of me, and I will make the nations your heritage, and the ends of the earth your possession. (Psalm 2:7-8)
The first chapter of Hebrews tells us plainly that this passage is about Jesus. Here, the Father is talking to the Son, inviting him to pray that the mission of God for the whole world would be fulfilled through him. No doubt Jesus pray this very psalm and probably more than once. And the Father has no doubt granted his Son's request.
And as if it weren't enough to see inside this inter-trinitarian dialogue, we are actually invited into it, invited to become participants in the story Father and Son are writing. In Romans 8, Paul says that we have been given the Holy Spirit, and that he is in fact the "Spirit of adoption." Now God is not just God but Father, as well. "And if children, then heirs—heirs of God and fellow heirs with Christ" (Romans 8:17). When we put these two passages together, it becomes clear that the nations are our heritage as well, the ends of the earth our privileged possession.
And though Christ is exalted on high and presently reigns, the promises are not yet fully realized, for there still remain nations which are unreached, and many peoples still deny him. As co-heirs, then, we are also co-missionaries, called to bring to into being the full administration of our older brother and king—to reach the nations with the gospel message. Do you see? He means to fulfill his promises to the Son through us.
Who will you pray for as a part of that mission today? Let the Spirit free your heart to pray to our Father with the confidence of the Son to whom we are united by faith.