"Now as they spoke to the people, the priests, the captain of the temple, and the Sadducees came upon them, being greatly disturbed that they taught the people and preached in Jesus the resurrection from the dead. And they laid hands on them, and put them in custody until the next day, for it was already evening. However, many of those who heard the word believed; and the number of the men came to be about five thousand" (Acts 4:1-4).
Here the persecution of the church begins. As Peter and John continued teaching the people, they were interrupted by the Jewish religious leaders (including the Sadducees who were materialists, not believing in the human spirit or resurrection from the dead). These leaders were greatly agitated by the apostles' doctrine, particularly the teaching concerning the resurrection from the dead (and the fact that they used Jesus as their example!) Consequently, they took Peter and John into custody until tomorrow since it was too late to have any sort of hearing that day.
However, in spite of this interference by the Jewish religious leaders, the church continued to grow! The rulers were already too late to contain the message, for many who heard the word of God believed (cf. Rom. 10:17) and obeyed the gospel message. In fact, the total number of men had grown to 5000 since Pentecost! Clearly, the word of God was being preached, received, and lived by many faithful Christians.
"And it came to pass, on the next day, that their rulers, elders, and scribes, as well as Annas the high priest, Caiaphas, John, and Alexander, and as many as were of the family of the high priest, were gathered together at Jerusalem. And when they had set them in the midst, they asked, 'By what power or by what name have you done this?'" (Acts 4:5-7).
On the next day, when the elite Jewish religious leaders gathered together (i.e., the 71 member Sanhedrin court), they put Peter and John in the middle of their council and asked them by what authority they acted. They wanted to know if the apostles were acting on their own initiative or if someone had directed their actions. They are looking for something--anything--by which they could accuse them (this explains the ambiguity in questioning).
"Then Peter filled with the Holy Spirit, said to them, 'Rulers of the people and elders of Israel: If we this day are judged for a good deed done to a helpless man, by what means he has been made well, let it be known to you all, and to all the people of Israel, that by the name of Jesus Christ of Nazareth, whom you crucified, whom God raised from the dead, by Him this man stands here before you whole. This is the "stone which was rejected by you builders, which has become the chief cornerstone." Nor is there any salvation in any other, for there is no other name under heaven given among men by which we must be saved'" (Acts 4:8-12).
Peter is not intimidated by the council (cf. Matt. 10:17-19). He knew he and John had done nothing wrong in healing this helpless man. He boldly declared that the man who was formerly lame was healed by the name or authority of Jesus! Peter is very specific in identifying which Jesus he is speaking of. It was Jesus the Christ (i.e., the Messiah) who was from Nazareth. There could be no mistaking whom Peter spoke of. This was the same Jesus whom the religious leaders had crucified, though God the Father had brought Him back to life! Although the Jewish religious leaders (the "builders," if you will) had rejected Jesus, He had become the "chief cornerstone" of the Lord's building, which is most certainly the church (cf. Matt. 21:42,43; Eph. 2:19-22; I Pet. 2:4-10). Indeed, Jesus is both the builder and foundation of the church, which is the spiritual temple of God (cf. I Cor. 3:11,16,17). So, although Jesus had been rejected by men (who did not properly identify Him as the "chief cornerstone"), He was greatly exalted by God (all in accordance with prophecy). Peter went even further in Acts 4:12 by saying that there was no way to be saved from sin except through Jesus (cf. John 14:6). There is no one else who can save--only Jesus--period! This message wasn't politically correct then and it certainly isn't now, but that doesn't diminish its truthfulness. Thus, to reject Jesus (as these leaders had done) was to reject the only way of salvation! What a bold message to deliver to such a hostile group as the Sanhedrin! Peter ("the rock") is a wonderful example of speaking the truth without fear.