What does Acts 12:5 mean?

Herod Agrippa I, king over Judea, Samaria, Galilee, and territories east of the Jordan River, has beheaded the apostle James and arrested Peter. He plans on executing Peter, as well, to reinforce the support of the Sanhedrin for his rule. But it is the weeklong Feast of Unleavened Bread, the time when the Jews celebrate their deliverance from slavery in Egypt. For whatever reason, Agrippa will wait until the holidays are over.

Although Peter has been arrested by the Sanhedrin, twice (Acts 4:1–22; 5:17–40), this is his first recorded altercation with the Romans. In fact, until this point the Romans seem to have ignored the church, thinking it is just another Jewish sect and poses no political threat to order (Acts 18:12–16). Between eight and fourteen years prior, the Roman governor Pilate crucified their leader, Jesus—not because He threatened any disruption to Rome's rule, but because the Sanhedrin threatened unrest if Pilate let Jesus live (John 18:28—19:16).

Pilate was indifferent to the wishes of the Jews so long as they didn't interfere with the performance of his job. Agrippa, however, is more invested in the people he rules and their religion. He kept Caligula from installing a statue of himself in the temple and reads to the people from the Mosaic law. He plans on killing Peter not to ensure rest but to build goodwill.

But the church is praying. God promises to hear, with a mind to act on the prayers of those who are righteous (Proverbs 15:29). Around this time, James, Jesus' half-brother, will write "The prayer of a righteous person has great power as it is working" (James 5:16). Peter will later affirm the sentiment (1 Peter 3:12). Acts 12:6–11 records God's answer to their prayers: Peter will be rescued, unscathed. That doesn't mean God grants all the request of His followers, and crucifixion is still in Peter's future (John 21:18–19). But, like the night of the storm (Mark 4:35–41), Jesus still has plans for Peter on earth.