Have you ever noticed how the Book of Acts starts:
In the first book, O Theophilus, I have dealt with all that Jesus began to do and teach, until the day when he was taken up, after he had given commands through the Holy Spirit to the apostles whom he had chosen. To them he presented himself alive after his suffering by many proofs, appearing to them during forty days and speaking about the kingdom of God. (Acts 1:1-3 ESV)
There are two things I want to point out: 1) Luke’s first book (the Gospel of Luke) dealt with “all the Jesus began to do and teach” which indicates that this book (Acts) deals with what Jesus continued to do and teach. 2) After Jesus’ resurrection, he talked to many people about the kingdom of God.
And the end of Acts, we read this passage:
He [Paul] lived there two whole years at his own expense, and welcomed all who came to him, proclaiming the kingdom of God and teaching about the Lord Jesus Christ with all boldness and without hindrance. (Acts 28:30-31 ESV)
Again, there are two things that I’d like to bring up: 1) Paul taught about Jesus with boldness and without hindrance even though he was under house arrest. 2) Paul, as with Jesus earlier, was proclaiming the kingdom of God.
Thus, at the beginning of Acts and the end of Acts (as well as several other places in the book – Acts 1:6, 8:12, 14:22, 19:8, 20:25, 28:23) we see the importance of speaking about and proclaiming the kingdom of God. Furthermore, we see that this type of proclamation is a continuation of what Jesus was doing and that the proclamation was unhindered even when the one proclaiming was imprisoned.
It seems, then, that Luke intended his second volume to be a treatise on the expansion of the kingdom of God. However, Luke did not intend Acts to be a treatise on the beginning of the kingdom. His Gospel explained that Jesus was the beginning of the kingdom of God. Similarly, Luke did not intend Acts to be a treatise on the end of the expansion of the kingdom. Instead, the kingdom continues to be proclaimed at the end of the book.
From just after Luke finished writing Acts until today, a reader would get the idea that the kingdom of God continues to expand and therefore must continue to be proclaimed. The reader would close the book seeing himself or herself as the one to proclaim the kingdom.
There are obviously other themes in the book of Acts (i.e. dependence on the Spirit, the kingdom community created by the Spirit, the gospel’s defeat of worldly systems), but we should never overlook the emphasis on the proclamation and expansion of the kingdom of God. This, along with many other aspects of the book of Acts, makes the book a missionary book, in the sense that those reading the book recognize that they are “sent” (apostello, missio).
So… you are sent to proclaim the kingdom of God and to see the kingdom of God expand.
(By the way, did you notice that we’ll only see this theme if we read the entire book, not just memorize one verse or passage?)