v1-4: Herod is a ruthless man, and an opponent of the church. He kills James, which "pleased the Jews," and doubtless strengthens his own position. Later, after Peter escapes from prison, he has four squads of soldiers put to death (v19).
He times his attack at Passover, an emotional time for both Christians and Jews.
v5: The Christians pray earnestly and constantly; indicating their concern for Peter. 'Corporate prayer unlocked miraculous provision into an impossible situation' (Mike Betts).
v6: Peter is asleep on the eve of his trial. He is at peace; just as Jesus slept in the boat in a storm.
v7-11: Peter is initially not sure at the reality of his deliverance, "he thought he was seeing a vision." Even so, God did not stop doing it; He is not limited by our unbelief. Ps 34.19 speaks of God's power to deliver; see 2 Pet 2.9.
v12-15: The Christians have met together in Mary's house to pray. Rhoda, who comes to the door is "so overjoyed," and the others hardly believe that Peter has been released. Again, their lack of faith does not despatch him back into the prison.
It has been suggested that the house was the same place as that where Jesus had celebrated the Passover with the disciples. This would provide the reason why the young Mark (Mark 14.51-52) later followed the disciples to Gethsemane.
v16-17: Peter's arrival brings great assurance to the Christians; here is real answer to prayer.
v18-19: The soldiers have no explanation, and Herod puts them to death.
v20: The events in Jerusalem coincide with the breach between Herod and Tyre and Sidon. These cities take the initiative while he is in Caesarea, and seek peace. Their actions encourage his pride and arrogance.
v21-23: Herod, like all rulers, is appointed by God, Rom 13.1. Yet the respect shown by the people of Tyre and Sidon goes too far, "This is the voice of a god, not of a man;" they worship him, and he accepts worship. So God strikes him down and kills him.
Here is further protection for the infant church, this time from an enemy outside. In 5.1-10, God took away Ananias and Sapphira, enemies from within. The Lord did not do such things during His earthly ministry, but there are a number of such judgments in Acts, including a number struck blind. See Ps 50.21, where the Lord will not keep silent, but will act in judgment.
v24: As a result of these things, God's word continues to spread.
v25: Saul and Barnabas fulfil their ministry, see 11.30. They are in Jerusalem while Peter is imprisoned, and while Herod visits Caesarea.