And when it was day ... - It is evident from the narrative that it was not contemplated at first to release them so soon, Acts 16:22-24. But it is not known what produced this change of purpose in the magistrates. It is probable, however, that they had been brought to reflection, somewhat as the jailor had, by the earthquake, and that their consciences had been troubled by the fact, that in order to please the multitude, they had caused strangers to be beaten and imprisoned without trial and contrary to the Roman laws. An earthquake is always suited to alarm the guilty; and among the Romans it was regarded as an omen of the anger of the gods, and was therefore adapted to produce agitation and remorse. The agitation and alarm of the magistrates were shown by the fact that they sent the officers as soon as it was day. The judgments of God are eminently suited to alarm sinners. Two ancient mss. read this, “The magistrates who were alarmed by the earthquake, sent, etc.” (Doddridge). Whether this reading be genuine or not, it doubtless expresses the true cause of their sending to release the apostles.
The serjeants - ῥαβδούχους rabdouchous. Literally, those having rods; the lictors. These were public officers who walked before magistrates with the emblems of authority. In Rome they bore before the senators the fasces; that is, a bundle of rods with an axe in its center, as a symbol of office. They performed somewhat the same office as a beadle in England, or as a constable in our courts (America).