Earthquake (seismo). Old word from seiw, to shake. Luke regarded it as an answer to prayer as in Luke 4:31 . He and Timothy were not in prison. So that the foundations of the prison house were shaken (wste saleuqhnai ta qemelia tou desmwthriou). Regular construction of the first aorist passive infinitive and the accusative of general reference with wste for actual result just like the indicative. This old word for prison house already in Matthew 11:2 ; Acts 5:21Acts 5:23 which see. Temelia is neuter plural of the adjective qemelio, from qema (thing laid down from tiqhmi). So already in Luke 6:48 ; Luke 14:29 . If the prison was excavated from rocks in the hillside, as was often the case, the earthquake would easily have slipped the bars of the doors loose and the chains would have fallen out of the walls. Were opened (hnewicqhsan). First aorist passive indicative of anoigw (or -numi) with triple augment (h, e, w), while there is no augment in aneqh (first aorist passive indicative of anihmi, were loosed), old verb, but in the N.T. only here and Luke 27:40 ; Ephesians 6:9 ; Hebrews 13:5 .