“Now when they heard this, they were pricked in their heart, and said unto Peter and to the rest of the apostles, Men and brethren, what shall we do?”
King James Version (KJV)
2:37 They said to the apostles, Brethren - They did not style them so before.
Ac 2:37 When they heard [this]. The conclusion, supported by such convincing demonstration. Before Peter began to speak they did not understand the signs; but now it was clear to them that they had rejected and crucified the Lord. Pricked in their heart. Convicted of their sins, and pierced with sorrow. They believed Peter's affirmation; their faith revealed their sin in rejecting Christ. Overwhelmed with sorrow, they ask, What shall we do? Is there any way that such sinners can be pardoned?