"But you shall receive power when the Holy Spirit has come upon you; and you shall be witnesses to Me in Jerusalem, and in all Judea and Samaria, and to the end of the earth." (Acts 1:8) The Acts of the Apostles is commonly read as a record of the growth and miracles of the early church. However, the core that the Bible intends to say through the Acts of the Apostles does not lie only in testifying to the work of the Holy Spirit. How the already completed gospel of the water and the Spirit was testified to the whole world, that is the central message of the Acts of the Apostles. This book explains the Acts of the Apostles from Chapter 1 to Chapter 28 from the perspective of the gospel of the water and the Spirit. It is a record following how the gospel of Jesus Christ—who had the sins of the world transferred to Him by receiving baptism from John, received the punishment of those sins on the Cross, and then resurrected from the dead—was testified. By reading this book, we come to confirm how the gospel of the water and the Spirit given by the Lord is propagated to the end of the earth. Furthermore, we will clearly receive testimony on how this gospel saves sinners from the sins of the world through the two structures of the baptism and the Cross.