In Acts Chapter 2 a few crazy things happen. Fist, The Holy Spirit cam upon them! This is a HUGE deal as in the past the Holy Spirit had dwelt behind the curtain in the temple (which you may remember was torn from top to bottom when Christ died – Matt 27:51). A new thing was happening as the Spirit would now dwell in the hearts of men. Second, Peter puts all the pieces together and clearly lays out the gospel to everyone present, explaining to them that this Jesus, whom they crucified, and whom God raised from the dead, was the Messiah God had promised David. Third, we see the Church come together, devoting themselves to the apostle’s teaching (Scripture) fellowship, breaking of bread (each other), and prayers. In short, we see them becoming “The Church!” This third crazy thing was only made possible by the first and second. As part of the body of Christ we are called unified, to put each ahead of ourselves and to act as one body. This is impossible to do apart from The Holy Spirit. We cannot call ourselves into it, we must surrender ourselves into it.
Read: Acts 1:8, 2:1-15, 2:16-28, 2:29-41, 2:42-47