What is the meaning of Acts 12:18-19?

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. (Acts 12:18-19 KJV)

William Burkitt’s Commentary

Observe here, 1. How wicked persecutors are mightily enraged, when their bloody purposes are disappointed. Herod having lost his prize, is so incensed, that he caused the keepers first to be examined, (and possibly by tortures) and then to be put to death.

Observe, 2. The justice of God, and the great injustice of Herod: It was just in God to suffer the soldiers, who were Herod’s instruments in persecution, to die by the bloody hand of Herod, whose tools they were. Instruments in persecution God oft-times meets with in this world, and sometimes they fall by the hands of persecutors themselves; yet was it notorious injustice in Herod to put to death those innocent soldiers, who could not help what was done, and were not ways accessary to the prisoner’s escape.