The setting of Peter's arrest in verse 3 is around the time of the Feast of Unleavened Bread/Passover - meaning it took place around the anniversary of Jesus' arrest and crucifixion. Peter is doing better this time than he did on that previous occasion. No denial now; he is prepared to die a martyr's death. But God had other plans in mind for Peter. What an appropriate time for a miracle of deliverance!
Was Peter a sound sleeper? The angel had to prod him in the side to wake him up. The night before his scheduled execution, and Peter is sleeping like a...rock.
Don't you just love Rhoda? Like a scene out of a modern sit-com, Rhoda goes to answer the door, hears that it's Peter on the other side, and in her joy leaves him standing outside while she goes back to report the good news! I love how this humorous detail was included in Acts!
Were Saul and Barnabas present at this moment? The episode takes place at the home of Mary, mother of John Mark. At the end of Acts 11, we are told that Saul and Barnabas had been sent to Judea with a gift. At the end of Acts 12, they return accompanied with John Mark. It would appear that they could be in Jerusalem during the events of Acts 12. It's not too big of a stretch to think that Luke had access to this story - and its eyewitness feel - from his later travels with Saul/Paul because Saul/Paul was there to see it for himself.
Herod dies a gruesome death because, according to the Bible, he was acclaimed by the crowd as a god and accepted that praise rather than giving the glory to the Lord God. There are many Herods running around in the New Testament era, but this appears to be Herod Agrippa I, nephew of the Herod (also known as Herod Antipas) from the Gospels who was ruling in the days of Jesus and had John the Baptist beheaded. Another Herod will make his appearance later in Acts, and he is believed to be Herod Agrippa II, son of this Herod from Acts 12. How did this Herod die? While it could be said that most people "die and are eaten by worms," in this case, Herod "was eaten by worms and died."