When St. Peter arose to address the people of Jerusalem on the day of Pentecost, he explained that the Resurrection of Christ was the fulfillment of prophecy. This was the first sermon to proclaim the gospel to the masses, delivered on Pentecost, the "birthday of the church." Peter's sermon, and other speeches in Acts of the Apostles, expressed and preserved crucial early Church traditions of how the crucifixion and resurrection were foretold by the prophets. It provides a snapshot of how the apostles evangelized their fellow Jews and provides important lessons for us as well