ANSWER: In Matthew 16:18, at the beginning of His public ministry, Jesus said, “I will build my church.” So, clearly, the church had not been built at that time. Ten days after Jesus ascended back to the Father, Peter on the day of Pentecost (Acts 2), for the first time, told people how to get into the church that Christ promised to build. On that day, three thousand people followed Peter’s instructions and their sins were forgiven (Acts 2:38-41). These, who were thus saved, were by that same process, the first to be added by the Lord to His church (Acts 2:47). This particular Pentecost day, then, was the birthday of the church of Christ!