Charles Ellicott Commentary Acts 16:33

"And he took them the same hour of the night, and washed their stripes; and was baptized, he and all his, immediately." — Acts 16:33 (ASV)

He . . . washed their stripes; and was baptized . . .—The two-fold washings—the one that testified to the repentance of the jailer and his kindly reverence for his prisoners, and the one that they administered to him as the washing of regeneration—are placed in suggestive juxtaposition. He, too, was cleansed from wounds that were worse than those inflicted by the rods of the Roman lictors.

No certain answer can be given to the question whether the baptism was by immersion or affusion. A public prison was likely to contain a bath or pool of some kind, where the former would be feasible. What has been said above (see Note on Acts 16:15) regarding the bearing of these narratives on the question of infant baptism also applies here, with the additional fact that those who are said to have been baptized are obviously identical with those whom St. Paul addressed (the word “all” is used in each case), and must, therefore, have been of an age to receive instruction together with the jailer himself.