The priests and the captain of the temple guard and the Sadducees came up to Peter and John while they were speaking to the people. (4:1)
Already the Jewish religious leaders were becoming uncomfortable with the message they were hearing about that was going around, that the old disciples of Jesus were spreading… and here they were again addressing a big crowd right out there in the temple courts; they must do something. It’s interesting that the Sadducees are mentioned here, but there’s no mention of Pharisees, but then Peter and the others were talking about Jesus, saying that He had risen from the tomb, and that was clearly an affront to the Sadducees who taught that there was no resurrection from the dead.
They had the Apostles arrested and thrown into jail for the night.
The next morning the Sanhedrin was convened and the men were brought forth for questioning. Clearly, they had reason to be concerned because even though they had broken up the address Peter was making to the crowd, a rather large group there had come to follow Jesus (4:4).