"And in these days prophets came from Jerusalem to Antioch. Then one of them, named Agabus, stood up and showed by the Spirit that there was going to be a great famine throughout all the world, which also happened in the days of Claudius Caesar. Then the disciples, each according to his ability, determined to send relief to the brethren dwelling in Judea. This they also did, and sent it to the elders by the hands of Barnabas and Saul" (Acts 11:27-30).
Claudius is the only Caesar mentioned explicitly by New Testament writers and he reigned from 41 - 54 A.D. Secular historians confirm a severe famine occurred during that period (cf. Suetonius, Tacitus, & Josephus). These verses show, once again, the loving and generous spirit of the early church. When a need arose or was anticipated prophetically (in this case a famine), disciples who had the means to offer assistance did so of their own free will. "Ability" can be defined here as having both the resources (cf. II Cor. 8:12) and opportunity to accomplish the task under consideration. The money for relief that was collected was then transported to Judea by Barnabas and Saul. They would take it to the elders (presumably of the Jerusalem church) who would then distribute it as needed. This is the first reference of elders in the church (obviously, they were appointed sometime previously in accordance with the divine requirements; cf. I Tim. 3; Titus 1). Having at least two men involved in the transfer of the funds was most expedient for accountability purposes. It is believed that the primary makeup of the church in Antioch at this time was Gentile. Thus, their generosity is even more significant for we have Gentiles helping Jews! It would seem the influence of the generous Barnabas rubbed off on them.
"Now about that time Herod the king stretched out his hand to harass some from the church. Then he killed James the brother of John with the sword. And because he saw that it pleased the Jews, he proceeded further to seize Peter also. Now it was during the Days of Unleavened Bread. So when he had arrested him, he put him in prison, and delivered him to four squads of soldiers to keep him, intending to bring him before the people after Passover" (Acts 12:1-4).
Although the initial motivation of Herod Agrippa behind his harassment of the church is not revealed, his continued persecution of Christians was encouraged because "he saw that it pleased the Jews." Not surprisingly, the Jews, who rejected Jesus Christ and the gospel message spread widely by the apostles and disciples, would find satisfaction in any government official making life difficult on Christians (particularly when they executed them!). Prior to this point, the persecution had come from the Jewish religious officials (and it seems possible they may have initially encouraged Agrippa's aggression against the church).
James, the brother of John, is the first apostle to be martyred (cf. Mark 10:39). He died by the sword (presumably via beheading). Although Judas Iscariot, after committing suicide, was replaced (in accordance with prophecy), there is no record of James being replaced as an apostle. Such points to the fact that the position of apostle was intended to be temporary in the church (as were the miraculous gifts) and not a permanent part of Christianity (unlike elders, deacons, and evangelists).
Herod was then emboldened to arrest Peter. He likely intended to put him to death also, but was delayed due to the Feast of Unleavened Bread (an execution would have seemed out of place at that time). In the meantime, he has Peter under guard by four soldiers at all time (sixteen total)! He is making sure (or so he thinks) that Peter will not escape! He doesn't want a repeat of what happened in Acts 5:19ff.