Part 1: Pentecost
The most sacred season of the Christian liturgical year surrounds the story of the resurrection of Jesus. Holy week, the week before Easter, chronicles Jesus' triumphant return to Jerusalem, his Last Supper with the Apostles, his betrayal by Judas, his trial and his execution on Good Friday. On Easter Sunday, the third day after his execution, Jesus rose from the dead and resumed teaching the Apostles for the following forty days. Forty days after Easter, he rose bodily to heaven as the Apostles watched. This day is known as the Ascension. Ten days after the Ascension, fifty days after Easter, is one of the most important days in the Christian calendar: Pentecost (meaning "fiftieth day").
In the liturgical calendar, Pentecost is as important as Christmas and nearly as important as Easter. Christmas was the birth of the Savior; Easter was his victory over death. Pentecost was the gift of faith, the power to believe and trust in God's preeminent love as expressed through sending to humankind his son, Jesus.
The family and friends of Jesus were together in Jerusalem. Jesus had risen from the dead, ascended into heaven, and said they would hear from him again. But it had been ten days and they were feeling lost and sad.
Suddenly, the spirit of God descended into them. They were filled with the Holy Spirit and spoke in unknown languages. Bystanders, people from many different countries, heard the disciples and understood them. They were amazed because everyone in the area was hearing the same story... but in their native tongues. It was as though a language translator program was being used. The disciples themselves were amazed. One of them, Simon Peter, realized this was the work of the Lord. He addressed a huge crowd gathered outside, speaking of Jesus Christ and the need to repent. Three thousand souls converted to Christianity in that public square in Jerusalem and were baptized in a single afternoon. This is an important milestone in the birth of Christianity. Many disciples went forth to preach about Jesus. Peter was important: he eventually went to preach in Rome and is considered the father of the Catholic Church.
Part 2: Damascus
It was also necessary to spread the word widely. In later chapters of Acts we hear of another important disciple. A man named Saul, who was persecuting Christians, was journeying to the city of Damascus to capture Christians and bring them before the courts. While on the road to Damascus, he had an encounter with Jesus that left him blind. After 3 days, Jesus spoke to a believer named Ananias and said he would work through him to cure Saul's blindness. Ananias was afraid because he knew Saul was searching for Christians to arrest, but he did as Jesus instructed and cured Saul in Jesus's name. Saul became a believer, was baptized, and started to preach about Jesus. He changed his name to Paul (remember prophets from the Hebrew Scriptures who changed their names after conversion?) and went on missionary trips to spread Christianity far beyond Jerusalem. Particularly, Paul felt inspired to convert Gentiles (non-Jews). Paul's actions were other milestones on the path to the founding of the Catholic Church. The phrase, "road to Damascus" has come to mean a dramatic, insightful turning point in someone's life.