The kingdom of God is a pretty big deal.
In Jesus’ first recorded sermon he said that, “the Kingdom of Heaven is near.”  When his disciples asked him how to pray, he instructed them to pray, “Father, may your name be kept holy. May your Kingdom come…”  And right before he leaves, the disciples ask, “Lord, are you at this time going to restore the kingdom to Israel?” 
The Kingdom was and still is a big deal. So what is it?
Scot McKnight defines kingdom this way: There are five elements of the term “kingdom” in the Bible: for there to be a kingdom (God’s kingdom), there must be a king (God, Christ), a rule (God rules redemptively and by governing or lordship), a people (Israel and the church), a law (Torah, the teachings of Jesus and life in the Spirit), and a land (holy land expands in the pages of the Bible). 
Essentially, that means that we are living in God’s kingdom here and now. We are living under the Kingship of Christ who rules his church by the teachings of his word through the Spirit.
Kingdom is not such an obvious term in Acts 2, but it is important. Peter, in his sermon to the crowd proclaims, “God has raised this Jesus to life, and we are all witnesses of it. Exalted to the right hand of God, he has received from the Father the promised Holy Spirit and has poured out what you now see and hear.”
In Acts 1, Jesus says to wait on the Holy Spirit. In Acts 2, we find Peter proclaiming that Jesus Christ is king and the pouring out Holy Spirit is a sign of reign. Jesus left us to do a mission. He left us to be the witnesses of his Kingship to the world. But, as Caleb Trimble wrote in Westbrook’s study guide for Acts, “There had to be something divine within us to make this possible. God created it, Jesus accomplished it, and the Spirit fulfills it. It is a beautiful trinitarian look at the Christian God. The prophecies have been fulfilled. The Kingdom of God will be established upon earth. The Holy Spirit will make it possible.”
Jesus brought the Kingdom and is now reigning. He left us as citizens of his spread the good news of what his kingship brings to the world and he gave us the Spirit so that we could do it.
Remember this week that you are a citizen of the King Jesus and tasked with sharing about his amazing kingdom. Remember also that you are not doing this alone under your own power, but through the power of the Holy Spirit.
May you walk this week in the Holy Spirit, the same Spirit who came down at Pentecost, so that the reign of Jesus Christ will be evident in your life so that you will be able to tell everyone the good news of Jesus.