1 Now about that time Herod the king stretched forth his hands to vex certain of the church.

[Herod the king] This was Herod Agrippa the first. There are six Herods mentioned in the New Testament. For a short description of the Herod family see A list of Herods in the Bible.

[To vex certain of the church] There had been a short pause in the persecution of the church, Acts 9:31, but at this point the persecution resumes.

2 And he killed James the brother of John with the sword.

[Killed James the brother of John] Herod struck at the leadership of the church beginning with James, the brother of John.

There are three men named James who were prominent in the early church.
1. James, the son of Zebedee, brother of John. An Apostle. Matthew 4:21-22. The one who was killed by Herod on this occasion.
2. James, the son of Alphaeus, also an apostle. Matthew 10:3.
3. James, the brother of Jesus. Not an apostle. Mark 6:1-4.
James did not become a believer in Jesus until sometime after the resurrection. John 7:5, Acts 1:14, Galatians 1:18-19.
We believe this is the James who exercised significant leadership in the early church. Acts 15:13-19, Acts 21:18.

[With the sword] Beheaded. We are told by early commentators that the Talmud specified beheading as the method of execution to be used upon those who caused people to be led away from the Jewish faith. This was the probable charge leveled against James.

3 And because he saw it pleased the Jews, he proceeded further to take Peter also. (Then were the days of unleavened bread.)
4 And when he had apprehended him, he put him in prison, and delivered him to four quaternions of soldiers to keep him; intending after Easter to bring him forth to the people.

[He proceeded further to take Peter] A good politician is always sensitive to what pleases his constituants. In this case the reference to The Jews is a reference to the Jewish religious leadership which was vehemently opposed to Jesus Christ and anybody who believed in him. Although legally under the rule of Rome and Roman appointees, the general populace preferred to follow the dictates of their religious rulers.

[Then were the days of unleavened bread] Passover and the week immediately following.. See the page on Jewish Feasts.
The reference to Easter is a mild mistake in translation. As the translators were attempting to put this verse into the common English language they decided to use the name of a current Christian holiday, Easter. Pesach, the combination of Passover, Unleavened bread and First fruits celebrated release from Egypt, wandering in the wilderness and arrival at the promised land, where Easter celebrates the resurrection of Jesus Christ. The resurrection of Christ was certainly not celebrated as a holiday by the Jewish leadership.

[Four quaternions of soldiers] Four sets of four soldiers who took turns guarding Peter during his stay in prison. Of a given set of four soldiers, two would be physically chained to Peter while the other two would stand guard at strategic locations such as prison doors leading into the area where he was kept.

5 Peter therefore was kept in prison: but prayer was made without ceasing of the church unto God for him.

[Prayer was made without ceasing of the church unto God] James had already been executed and it seemed that the same fate awaited Peter unless the Lord God intervened. Prayer was the correct course of action.
Matthew 21:21-22, John 16:23, Romans 8:26.

6 And when Herod would have brought him forth, the same night Peter was sleeping between two soldiers, bound with two chains: and the keepers before the door kept the prison.
7 And, behold, the angel of the Lord came upon him, and a light shined in the prison: and he smote Peter on the side, and raised him up, saying, Arise up quickly. And his chains fell off from his hands.
8 And, the angel said unto him, Gird thyself, and bind on thy sandals. And so he did. And he saith unto him, Cast thy garment about thee, and follow me.
9 And he went out, and followed him; and wist not that it was true which was done by the angel; but thought he saw a vision.

[And behold the angel of the Lord] At that time prisons were merely warehouses for storage of persons deemed unfit for circulation in normal society. There was no good reason to provide amenities for such people, therefore prisons were often basement dungeons; dark, unventilated and unsanitary. Peter had for comfort removed some of his outer garments and was sleeping, chained between two guards. The angel came, put the guards into a deep sleep, provided light (probably emanating from his own presence), awakened Peter and told him to get dressed and put his outer cloak around him. The chains fell off and the two of them proceeded to walk out of the prison. No violence, just the power of God. What appears difficult to us from our earthly perspective is but a simple exercise for God. Matthew 28:18-20.
Peter thought he was dreaming.

10 When they were past the first and the second ward, they came unto the iron gate that leadeth unto the city; which opened to them of his own accord: and they went out, and passed on through one street; and forthwith the angel departed from him.
11 And when Peter was come to himself, he said, Now I know of a surety, that the LORD hath sent his angel, and hath delivered me out of the hand of Herod, and from all the expectation of the people of the Jews.
12 And when he had considered the thing, he came to the house of Mary the mother of John, whose surname was Mark; where many were gathered together praying.

[And when Peter was come to himself] Then Peter realized it was not a dream. He was a fugitive, so it would be a good idea to find a place of shelter, off the street. He went to the home of Mary, mother of Mark, author of the Gospel according to Mark, where many of the church had gathered to pray. One might be tempted to say, "By coincidence," but we know it was by design of the Holy Spirit.

13 And as Peter knocked at the door of the gate, a damsel came to hearken, named Rhoda.
14 And when she knew Peter's voice, she opened not the gate for gladness, but ran in, and told how Peter stood before the gate.
15 And they said unto her, Thou art mad. But she constantly affirmed that it was even so. Then said they, It is his angel.
16 But Peter continued knocking: and when they had opened the door, and saw him, they were astonished.

[And as Peter knocked at the door of the gate] Here Mark had a first-hand confirmation of what Jesus had taught regarding prayer and faith. Mark 11:23-24, Luke 17:5-6.
The faith exercized was tiny indeed. One can imagine the scene.

"Oh Lord, please let Peter out of prison."
"Peter is knocking at the door!"
"You're crazy! Peter is in prison. Oh Lord, please let Peter out of prison."

17 But he, beckoning unto them with the hand to hold their peace, declared unto them how the Lord had brought him out of the prison. And he said, Go shew these things unto James, and to the brethren. And he departed, and went into another place.

[Go and show these things unto James] James, the brother of John had been executed by Herod. The James referenced here was probably James, brother of Jesus.

18 Now as soon as it was day, there was no small stir among the soldiers, what was become of Peter.
19 And when Herod had sought for him, and found him not, he examined the keepers, and commanded that they should be put to death. And he went down from Judaea to Caesarea, and there abode.

[There was no small stir among the soldiers] On two levels. How could this have happened? Peter had once before been miraculously released from this prison. Had it happened again? Acts 5:17-23. Secondly, Nobody would believe them. They would pay with their lives.

[And he went down from Judaea to Caesarea.] Caesarea was the preferred residence of the Herods who ruled Judaea. They went up to Jerusalem as business required but soon retreated again to the seaside palace.

20 And Herod was highly displeased with them of Tyre and Sidon: but they came with one accord to him, and, having made Blastus the king's chamberlain their friend, desired peace; because their country was nourished by the king's country.

[They came with one accord to him] That is, emissaries from Tyre and Sidon. In Jerusalem Herod was conscious of the grudging submission of the Jews, but in Caesarea, home of the Roman 10th legion, he was treated as a true king.

21 And upon a set day Herod, arrayed in royal apparel, sat upon his throne, and made an oration unto them.
22 And the people gave a shout, saying, It is the voice of a god, and not of a man.
23 And immediately the angel of the Lord smote him, because he gave not God the glory: and he was eaten of worms, and gave up the ghost.

[It is the voice of a god] The king thoroughly enjoyed and willingly accepted the praise of men, however insincere it might be. But the "Voice of a god" was silenced when it failed to acknowledge the true God.

24 But the word of God grew and multiplied.
25 And Barnabas and Saul returned from Jerusalem, when they had fulfilled their ministry, and took with them John, whose surname was Mark.

[Barnabas and Saul returned from Jerusalem,] The church at Antioch had sent Barnabas and Paul to the church at Jerusalem with a gift to provide relief during the anticipated famine. Acts 11:27-30. Having delivered the gift and greetings from the church at Antioch, Barnabas and Paul returned to continue their ministry in Antioch, taking John Mark with them. It is possible that John Mark was Barnabas' nephew. Colossians 4:10.