“Therefore let all the house of Israel know assuredly that God has made this Jesus, whom you crucified, both Lord and Christ.” Now when they heard this, they were cut to the heart, and said to Peter and the rest of the apostles, “Men and brethren, what shall we do?”
Peter’s sermon proved from the Old Testament that Jesus was the Messiah, and God opened the minds of many in his audience to not only believe this, but to see the implications for themselves. Though many of them were not directly involved in Christ’s crucifixion, Peter’s words implicate us all—our sins are the reason He gave His life.
They were convicted and deeply desired to do whatever they could to be forgiven and to change. This is the attitude that God looks for and can work with (Isaiah 66:2). This attitude is the beginning of the conversion process.