2:36 “Therefore let the entire house of Israel know with certainty that God has made him both Lord and Messiah, this Jesus whom you crucified.”
2:37 Now when they heard this, they were cut to the heart and said to Peter and to the other apostles, “Brothers, what should we do?”
2:38 Peter said to them, “Repent, and be baptized every one of you in the name of Jesus Christ so that your sins may be forgiven; and you will receive the gift of the Holy Spirit.
2:39 For the promise is for you, for your children, and for all who are far away, everyone whom the Lord our God calls to him.”
2:40 And he testified with many other arguments and exhorted them, saying, “Save yourselves from this corrupt generation.”
2:41 So those who welcomed his message were baptized, and that day about three thousand persons were added.
Peter and the other apostles were so invigorated by the appearance of Christ and the power of the Holy Spirit that the massive crowds, who came to celebrate Pentecost, were in owe of their preaching and witness of the Lord. Moreover, Peter was armed with a new perspective of how the Jewish scriptures foretold of the coming of Christ. With power of the Spirit and the wisdom of the scriptures Peter was able to convince many in his audience to repent of their sins and to be baptized. According to the book of Acts it was about 3,000 people.
While we have a slightly different context today, we are still called to have a witness in the power of the Holy Spirit. We have an advantage today, in that we have the whole New Testament as a witness to communicate with others. We also have about 2000 years of Christian thought and philosophy to study and give us understanding. In addition, the Christian population in the world is quite large. There is no shortage of workers in the harvest.
However, these advantages can sometimes be hurdles for us. We can become complacent in our walk with Christ. Our faith can become routine and we can become lackadaisical. Therefore, we must stay awake and vigilant so that we can have an affective witness, not one of mere obligation either. We must seek the power and guidance of the Spirit and obey the call of the Lord, wherever He leads us.