Acts 4:5-12

On the next day, their rulers and elders and scribes were gathered together in Jerusalem; 6 and Annas the high priest was there, and Caiaphas and John and Alexander, and all who were of high-priestly descent. 7 When they had placed them in the center, they began to inquire, “By what power, or in what name, have you done this?” 8 Then Peter, filled with the Holy Spirit, said to them, “Rulers and elders of the people, 9 if we are on trial today for a benefit done to a sick man, as to how this man has been made well, 10 let it be known to all of you and to all the people of Israel, that by the name of Jesus Christ the Nazarene, whom you crucified, whom God raised from the dead — by this name this man stands here before you in good health. 11 “He is the STONE WHICH WAS REJECTED by you, THE BUILDERS, but WHICH BECAME THE CHIEF CORNER stone.  12 “And there is salvation in no one else; for there is no other name under heaven that has been given among men by which we must be saved.”

Immediately after Peter (with John) gave his message to the people (Acts 3:11-26), priests, the captain of the temple guard, and the Sadducees came and put Peter and John in jail for preaching about Jesus (mainly for proclaiming His resurrection; for the Sadducees did not believe in the resurrection).

On the next day (v. 5), they questioned Peter and John as to what gave them the authority to speak about Jesus the way they did. Well, I imagine that Peter immediately recognized his open door to preach to them. And Peter was indeed filled with the Spirit and held nothing back, He proclaimed Jesus as the healer of the sick man and as the chief cornerstone which they rejected. Then, to put a cap on it, Peter told them that they could be saved by no other name except by Jesus Christ. Peter certainly was filled with the Holy Spirit—which became evident by his great boldness.