The sermon traces the transition from Jesus's earthly ministry to the early church, focusing on the book of Acts as a continuation of Luke's Gospel. It examines the significance of the former treatise, referencing Luke's Gospel, and highlights the importance of understanding the context of the apostles' actions following Jesus's ascension. The discussion centers on the fulfillment of prophecy concerning Judas's betrayal and the subsequent selection of Matthias to restore the number of apostles to twelve, emphasizing the divine appointment of leaders and the ongoing mission to witness to Jesus's resurrection and the power of the Holy Spirit.