It may surprise some Christians to realize that the Holy Spirit is dispensed very sparingly in the Old Testament. It's given to certain people, typically leaders of Israel, or King David for a period of time. What happens when we come to Pentecost and the church after Jesus' ascension and the gift of the Spirit is what we might call the "democratization" of the Spirit, the gift of the Spirit to all believers. That's important for a number of reasons. Firstly, it's important because God made a promise in Joel chapter 2 that in the last days, that is, when God's purposes had come to a fulfillment, when God's kingdom had come, a sign of that would be the gift of the Spirit on all people. And that's exactly the passage that Peter quotes at Pentecost in Acts chapter 2. So, it's important because it's a gift and sign of the new covenant. Secondly, it's important because the Holy Spirit is given to empower us for mission, and so that's why the apostles were told to wait in Jerusalem until the gift of the Spirit came, and when the gift of the Spirit came, they were sent out into mission. So, the importance of the Spirit is that all believers have the Spirit, it is the last days, the kingdom of God has come, but with that is the impetus and the command and the power to mission.