Just before this the jailer had drawn his sword to kill himself, thinking the prisoners had fled (Acts 16:27). Now he came "trembling" and fell down before the men he had locked in the stocks (Acts 16:29). Barnes says, "Never was a more important question asked than this," and he holds that the jailer was asking about eternal salvation, not just escape from punishment, as the apostles' answer shows. Matthew Henry writes that "His salvation is now his great concern, and lies nearest his heart, which before was the furthest thing from his thoughts." Gill notes that the jailer, thinking "upon the foot of works," assumed he must do something to be saved.

Paul and Silas answered directly: "Believe on the Lord Jesus Christ, and thou shalt be saved, and thy house" (Acts 16:31). They "spake unto him the word of the Lord, and to all that were in his house" (Acts 16:32). That same hour he washed their stripes and "was baptized, he and all his, straightway" (Acts 16:33). He set food before them and "rejoiced, believing in God with all his house" (Acts 16:34).

Philippi was "the chief city of that part of Macedonia, and a colony" (Acts 16:12). Paul and Silas were there because the masters of a fortune-telling girl lost their income when Paul cast out the spirit, and they dragged the missionaries before the magistrates (Acts 16:16-22). The magistrates had them beaten and charged the jailer "to keep them safely," so he put them in the inner prison with their feet in the stocks (Acts 16:23-24). Barnes explains that a jailer would face punishment if prisoners escaped, which is why he drew his sword (Acts 16:27).

The girl had cried for days that these men "shew unto us the way of salvation" (Acts 16:17). Barnes lists that cry, the earthquake, and the jailer's sense of guilt for imprisoning them among the things that may have stirred the jailer's question.

God was at work in the darkest place in Philippi. Paul and Silas, beaten and chained, "prayed, and sang praises unto God" at midnight, and "suddenly there was a great earthquake" (Acts 16:25-26). The earthquake opened the doors, but the gospel opened the jailer's heart.

The answer to his question is short. Barnes calls it "a simple, a plain, and an effectual direction," and Matthew Henry calls it "the sum of the whole gospel, the covenant of grace in a few words." The man who asked what he must do was told whom to believe. The man who was about to take his own life ended the night rejoicing with his whole house (Acts 16:34).