Into the inner prison (eis tēn esōteran phulakēn). The comparative form from the adverb esō (within), Ionic and old Attic for eisō. In the lxx, but in the N.T. only here and Heb 6:19. The Roman public prisons had a vestibule and outer prison and behind this the inner prison, a veritable dungeon with no light or air save what came through the door when open. One has only to picture modern cells in our jails, the dungeons in feudal castles, London prisons before the time of Howard, to appreciate the horrors of an inner prison cell in a Roman provincial town of the first century a.d.
Made their feet fast (tous podas ēsphalisato autōn). First aorist (effective) middle of asphalizō, from asphalēs (safe), common verb in late Greek, in the N.T. only here and Mat 27:64. The inner prison was safe enough without this refinement of cruelty.
In the stocks (eis to xulon). Xulon, from xuō, to scrape or plane, is used for a piece of wood whether a cross or gibbet (Act 5:30; Act 10:39; Act 13:29; Gal 3:13; 1Pe 2:24) or a log or timber with five holes (four for the wrists and ankles and one for the neck) or two for the feet as here, xulopedē, Latin vervus, to shackle the feet stretched apart (Job 33:11). This torment was practiced in Sparta, Athens, Rome, and Adonirom Judson suffered it in Burmah. Xulon is also used in the N.T. for stick or staff (Mat 26:47) and even a tree (Luk 23:31). Tertullian said of Christians in the stocks: Nihil crus sentit in vervo, quum animus in caelo esto4 (Nothing the limb feels in the stocks when the mind is in heaven).