Albert Barnes Commentary Acts 16:27

"And the jailor, being roused out of sleep and seeing the prison doors open, drew his sword and was about to kill himself, supposing that the prisoners had escaped." — Acts 16:27 (ASV)

Would have killed himself. This was all done in the midst of agitation and alarm. He supposed that the prisoners had fled. He presumed that their escape would be charged on him. It was customary to hold a jailer responsible for the safekeeping of prisoners, and to subject him to the punishment due to them, if he allowed them to escape.

See Acts 12:19. It should be added, that it was common, and approved among the Greeks and Romans, for a man to commit suicide when he was surrounded by dangers from which he could not escape. Thus Cato was guilty of self-murder in Utica; and thus, at this very place at Philippi—Brutus and Cassius, and many of their friends, fell on their own swords, and ended their lives by suicide.

The custom was thus sanctioned by the authority and example of the great; and we should not be surprised that the jailer, in a moment of alarm, should also attempt to destroy his own life. It is not one of the least benefits of Christianity, that it has proclaimed the evil of self-murder, and that it has done so much to drive it from the world.