Do thyself no harm (mhden praxh seautwi kakon). The usual construction (mh and the aorist subjunctive) for a prohibition not to begin to do a thing. The older Greek would probably have used poihsh here. The later Greek does not always preserve the old distinction between poiew, to do a thing, and prassw, to practice, though prassete keeps it in Philippians 4:9 and poiew is rightly used in Luke 3:10-14 . As a matter of fact prassw does not occur in Matthew or in Mark, only twice in John, six times in Luke's Gospel, thirteen in Acts, and elsewhere by Paul. Sprang in (eisephdhsen). First aorist active of eisphdaw, old verb, but here only in the N.T. Cf. ekphdaw in Luke 14:14 . The jailor was at the outer door and he wanted lights to see what was inside in the inner prison.